Wow that sucks...if I were you I'd cut your small loss and learn from it & keep the contract as a reminder of an 'almost' possible disaster.....I'm not a breeder but if I WERE ... I would want someone who buys a puppy to be able to AFFORD it...
if he couldn't make his bills and was bouncing checks - what would happen if he needed to take the puppy to the emergency vet ? Heck - just the NORMAL Vet can be expensive with Shots and tests...and food ? Heartworm meds ? Groomers ?
and don't forget the most important thing - TOYS and CLOTHES ! Lol ...just kidding
He had some big ones even asking you to hold a puppy that long for him - if it were me - I'd be WAY too attached to ever let it go
I would be glad he bought the other puppy and is out of your hair now.