Foster puppy from breeders- who broke into our house and took the pup to sell?

They sound like some really shady backyard breeders to me. For starters, responsible breeders do not ask people to foster a puppy that is returned to them. They take the time to work with them and make them suitable for another home, not p the burden onto someone else. I really don't know what to tell you. I'd say change the locks, cut your losses and never speak to these people again. But let everyone know what a shifty operation they're running.