
I had a return to me for the life-time of the dog clause in my Sale Contract, but as suggested, most of the time these Sale Contracts 'aren't worth the paper they are written on'. But at least it shows Intent!!
I homed one, an older bitch that wasn't up to breeding/showing standards. She went on a return to me agreement and unfortunately it wasn't a good home, once their Squaddie son returned and started kicking a football around, apparently AT her and she spooked. They contacted me, thank goodness, and we went and got her back. I told them I'd refund the small charge I'd made for her (as she was an older bitch) once I had a new home for her, so minus a minimal boarding fee. They seemed ok with that but later came back and told me they wished they'd rehomed her as 'they would have got a lot more for her'!! Clearly they'd been talking to somebody. Thank goodness I got her out of there, and quickly into a super new home.
I hope you can get your puppy back if you can, and sort out the details later would be my advice. And you are right re the being able to see him on a regular basis not being a good idea. We homed another hound, a male, after he started fighting with his uncle - and left him to settle in for about a month before we went to his new home to check all was ok with him. It would be very hard on any dog for the original owner to keep turning up, and going again.