Litter of (only) two pups: Last Sunday ((6 days ago) my two puppies (both males) were picked up by their new families.  I maintained extensive contact with both parties during the entire 10 weeks the puppies were with me (and my 6 dogs, including their mother and father).  Because there were only two in the litter, I gave them a lot of freedom, and they were more or less integrated into the "family" (myself and my dogs), although sleeping togther with their mother in the pen in the livingroom (while I slept upstairs with the other dogs).  This is a small bichon breed.  I have been breeding this breed since 1995 and have raised over 200 puppies.
One of the brothers seems to be having real problems adjusting to his new home.  I have never encountered this before in all the years I have been breeding.  It is a retired, very active, very nice and intelligent, dog-experienced couple, with all the time and dedication in the world.  The puppy, however, is exhibiting severe signs of stress, and I am very concerned.  He chews his front paws, he chases his tail, he scratches a lot, he wolfs down his food, he bites (in play) their hands and fingers and legs, he is apparently constantly on the go, all things he basically never did here at home.  He and his brother were, of course, constantly together, as all puppies tend to be.  I have not heard of any such behavior from the brother, and I am in close contact with both of the new owners of the two pups.
How can this little guy best be helped?  I have suggested distraction (instead of any kind of scolding), I've suggested feeding him from hand (instead of letting him gobble up his food in some sort of panic and to further the bonding procedure), he sleeps - as I suggest (firmly) to all my puppy-buyers - in a soft crate next to their bed, so he is not isolated. 
Do you think he is simply at a loss and totally insecure due to his brother's absence?  Any suggestions appreciated.  Thanks.

Have they changed his food? as it sounds food related to me .

No.  I always make sure that the new owners have exactly the same food on hand, in this case Acana Puppy Small Breed.  So no change whatsoever in the food.  That's why I tend to think that his food is his only connection to the life he lead at my home and just left.  Perhaps it gives him security...?

What about treats?

Hmm have they wormed him? maybe a wormer could be causing a reaction or vaccination or as gundogs suggested maybe they are giving treats which don't suit him or maybe something household as cleaning or washing products which they may of washed his bedding in?

Thanks to all for your thoughts.  No, they have not wormed him.  He was wormed by me (every two weeks together with their mother, and each time a different wormer), and the new owners will now have to set up their own worming schedule with their own vet.  I don't like to worm any more than necessary.
I tend to think that he simply misses his brother.  "Someone" is missing, and he can't find him!  And this causes great frustration and anxiety. I don't know what can be done about that except to wait and hope that time will work its effects.  I am put in mind of twins (humans) and how closely bonded they usually are.  Perhaps this took place in this litter, there being only two puppies.  I judged this puppy as the more sensitive of the two.

Gundogs:  I've been thinking about this.  Normally, I advise new owners to shun treats altogether and to save them for real training later on.  Treats can cause a vicious circle of food refusal and the puppy's simply holding out for the stuff he prefers.  But in this situation, I am wondering if the risk of the above might be worth it, as treats could give him new pleasure and perhaps that might induce confidence and relaxation....

As this pup is so used to being with other dogs, do they know a vaccinated, healthy dog that might visit ? Perhaps he is missing canine company.

Have you thought of a SnugglePup?  It is a soft toy which has a warmer inside and a realistic heartbeat - it helps puppies not feel alone in their new homes:  https://www.amazon.co.uk/SmartPetLove-Snuggle-Puppy-Behavioral-Golden/dp/B000S753WK/ref=sr_1_1?keywords=snuggle+pup&qid=1580571848&sr=8-1

It's possible it could be the water try bottled water for a few weeks to see if any difference in chewing himself.
Otherwise it sounds like he's taking advantage of being alone.

Poor pup, think his people need to interact more & get him to engage his brain.

The puppy "nipping"is to be expected as pups learn by using their mouths.

Suffle mat for his feeding ??? Make him work for it & slow him down.

Short bits of clicker training, no more than 5 mins max. Get them to look up KIKOPUP on Youtube

Treats are  a wide area. Have they given him safe things to chew on ?
As they will be doing some basic training now using part of his normal.food allowance would be in keeping with your advice  and also any training will keep his mind occupied
I wonder if there is anything in the new house that is irritating his skin making him itchy? I know its only a week but could be long enough for a reaction
Has a vet taken a look just in case there is any sign of a physical reason for his apparent itchy/ chewing himself.

Snuffle mats are great and work well with kibble .actually anything  that makes him have to work a bit for his food rather than just an open bowl.  Even just sprinkling it around a small area to go looking for is good  too

Furriefriends:  Yes, he does, of course, have a great many toys to chew on and play with.  I don't like chews such as rawhide or squizzles, as they can cause diarrhea or even get choked on. 

These people have had the same breed before, a male who lived to be over 15.  They have retired to Madeira, where they enjoy the mild but not overly-hot climate and the walks and hiking on that lovely island.  Right now they are in the house they own here in Switzerland, about 2 hours from me by car.  In one week, they will visit me with the puppy so that we can go together to MY vet, who is in possession of a combined vaccine:  the second of the 3 initial vaccinations plus rabies.  Not every vet has this on hand, but mine does, and it enables the people to return to Madeira far sooner than would otherwise have been possible.  We checked it out thoroughly with the international regulations, and all is in accordance.  After the vaccination next week (at 12 weeks), they must wait 21 days before leaving the country.  This vet appointment next week (Monday, Feb. 10) will give us a good opportunity to talk to my vet, should the adjustment problems still be there.  I can only imagine that it is a case of missing the brother (they were like "twins"), but I have had litters of only two several times and never had anything similar.  Also, extremely small breeds have litters of two fairly often, I should think. 
Yesterday, they took the puppy to the puppy play hour, at my suggestion, even though I felt it might be a little early for this.  But there is a trained leader there, and it might be good to talk to her.  I will hear from them today.  Many thanks for your remarks and suggestions!

Totally agree about rawhide etc horrid dangerous things that shouldn't be marketed .
Great that your own vet who u have confidence in can be talked to and i hope he settles soon

Yikes.   The vet is going to give the second set of vaccination + rabies at the same time?   I'd not want that.   When living abroad, we didn't have rabies done until 4+ months.

Totally agree MamaBas.  If they need the rabies to take the pup abroad sooner, then they should get only the rabies done now and they can get a final booster of the core vaccines (if needed) after they are in their destination country and several weeks after the rabies.

Hi Mamabas,  I know, and it is not the usual, which is just as you say.  Nevertheless, I have encountered this combi-vaccine in Austria and now here in Switzerland.  It is only for special reasons, I guess.  But the post I am going to write now eliminates the whole thing anyhow.

I want to tell you that, as I somehow - somewhere suspected might happen:  the puppy is on his way back to me.  The people feel that they cannot (and perhaps don't want to) cope with the needs and habits of such a young puppy.  They admit that they probably entertained unrealistic ideas of how it "was going to be", based on their experiences in the past.  But meanwhile, they are 16 or 18 years older, and maybe they didn't take this into account.  I too was led astray by their previous experience with several dogs (from puppyhood on) and by their open, honest, and very kind manner.  It has not worked, and probably my puppy felt that, somehow.  Although initially a shock, I am very glad he now comes back to me (in a few hours!), and he can stay as long as it takes to find him the right home.  The report about his brother couldn't be better!  I spoke with the new owner just now.

I did think that might be the case as I was reading your posts.  If you are used to being a one dog family and with hopefully a long living dog then in the 14 years or so you forget just how demanding a puppy is.  You go from a slow, sleeps a lot, not many needs kind of dog to your life being turned upside down and things not quite going to plan.  Thank goodness the pup has you to turn to.  Good luck finding the right home for him.

Just read your post and it sounds like this was the best for everyone. Hopefully now he is home with you it will allow you to properly see how he is and hopefully all will be well with his next home.
A pat on the back to your too for being such a good breeder

Phew!  Sounds like the best decision for the pup - and for your peace of mind.

He's lucky to have you to come back to.  It will be interesting to see how he is with you when he returns.

Good luck with finding his forever home in due course.

onetwothreefour:  I honestly did not know that this was an option.  Nobody suggested it.  I'm glad to know for perhaps another time, as I too would prefer to do it this way.

Good luck with the return.  If his litter-mate has already gone to his new home, that's good because being back with him, if this was to do with having been bonded with him, hving them together again could have compounded this issue.

I have a feeling this boy may have realised he wasn't THAT welcome in his new home, and have been reacting?

Perfect result I'd suggest and there will be a forever home for him, just waiting round the corner.

At least you be able to watch him yourself and see any issues if there is any.

I think this was the best outcome for the puppy and I’ve glad his owners realised it wasn’t going to work out and came back to you.

I don’t know how old your owners were, but we bought a new puppy when I was 62 and hubby 65. We were reasonably fit and puppy savvy having had a number over the years, but we had just had a break of 6 months between our last dog dying and the new one. Also it had been 15 years since the last puppy who had an older dog to play with and annoy instead of me.
I prepared beforehand by cleaning the house from top to toe, did all the washing and ironing and filled the freezer and cupboards with either ready meals or easy to make meals. It paid off very well. I was able to give my full attention to the little nippy monster and make headroads into training and house training. She was extremely hard work as she was the usual right pain in the neck during the evenings, nipped for England and firmly believed that sleeping during the day was for wimps.

Now she is the most lovely dog you could wish for.

Mamabas:  thanks for your very appreciated words.  Interesting, what you point out about the brother not being here.  You are certainly right:  better that he has gone.  I think my puppy did indeed feel the "not-rightness" about the situation.  He was there 6 days in total. Since he's been home, he has not chewed his paws nor chased his tail even once.  He behaves like a perfectly normal 11-week-old, very healthy puppy.  I am so happy to see him here, safe and well and feeling good about himself.  But the people who brought him back today were truly devastated.  I felt really bad for them.

In Response to Jodi

Lovely.  Thanks!

It’s nice to know he’s happy again. Thanks for the update.

Glad you're getting him back, reading your initial post I was thinking he sounds just like a normal puppy, they've forgotten how much work they are. You wouldn't have noticed so much at home as he had his brother to play with, but I bet they were playing almost all the time. The scratching is normal for pups wearing a collar for the first time, or a new collar. Wolfing food down - great, that's so much better than a pup who won't eat. Nipping them - perfectly normal. Chasing his tail, most puppies discover this fun (usually short lived) game.

I'm sure you'll find him his perfect home soon and this wee trip away can just be viewed as a bit more socialisation, another new experience for him.

Nimue, sorry, only I've just seen this. I wasn't actually meaning treats for training in this case. I was wondering if they had been giving him lots of treats, perhaps full of additives, which were making him giddy?
Anyhow, I'm pleased to see your update and hope it works out for you x