So, many of you know about the pup that was returned to me after a week of being in his new home.
Well it turns out that he has a very high temperature and is suffering from a UTI!
After the initial craziness calmed down (slightly) from coming back I started to notice that he was urinating constantly and he went six times in an hour out with me in the garden.
I took him to the vets who took his temperature and advised it was really high, checked him out and diagnosed a UTI.
Apparently, a combination of his stress levels, coupled with being on wet bedding and the fact that if stressed they don't clean themselves as much/properly has all caused this issue.
Poor little mite.
He has had an antibiotic jab and is now on a course of tablets for five days. He will then have another urine sample tested after five days off the antibiotics to ensure he is clear.
What a crazy situation!
He is beginning to calm down but is VERY attached to me, which I'm thinking will make the future rehoming process a little difficult.
But hey oh, hopefully he is on the road to recovery, albeit a longer one than I anticipated.

Poor chap hope he gets over uti then back on recovery
sounds like he had horrifc experince in novices hands

This is very interesting - is the inference that he had this when he was away (rather than it developing at your home since he returned)?  As in perhaps the stress of the move from your home left him not cleaning himself and then he became ill within a few days of them having him?  And perhaps then as the infection took hold he became more and more unmanageable?

I am just wondering because if he is peeing 6 times an hour no wonder the brief-owners couldn't keep his bedding dry, and if he was in discomfort/pain no wonder he was running about frantic and mouthing them terribly.  And if he was peeing constantly he was probably crated a lot because all the proponents of crating bang on at new puppy owners about how they won't soil their bedding (illness obviously notwithstanding and they often don't mention that in the books).  I can imagine him being very very hard to manage if he was in pain all that time, perhaps that's why they couldn't cope?  Did a vet see him when he was with them (even a new-puppy check type thing?)?  Are you going to let them know?  I think if this had happened to me, as a buyer, i would want to know, as it might solve the mystery enough that i'd want to give it another go.  I imagine they returned him to you in despair...

Good points poodle noodle. I guess if they are novice owners even saying to vet he is having accidents may not alert anyone to the problem. After all a young pup wont be housetrained so easy to miss that its abnormal what's happening. Poor little lad glad he is being sorted and will feel better soon

I have certainly squirrelled this thread away in case something similar befalls us furriefriends! Such difficult circumstances, very unlucky and upsetting for all. I expect if he was seen by a vet, in addition to "he's peeing everywhere" not being very remarkable for a 9-10week old, the vet probably figured having come from a good breeder and vet-checked before coming home, he was most likely healthy. One doesn't expect a well bred KC registered puppy from a decent breeder to be ill, and first-time puppy owners often have strange expectations about behaviour, easy for the vet to dismiss.

Yes I have let the owners know but they haven't even replied to my email.
Your right it could have occurred after the initial leaving home. He was vet checked and temperature before he left and in my contract it states pup needs to be vet checked within one working day of them acquiring him but they have not confirmed to me that they did this.

Hoping he recovers quickly and it's a one way street to a settled puppy and loving new future home.