Hi Josie
I don't mean to upset you in what is already a difficult situation, but it doesn't matter if it was an accidental mating, a one-off mating a litter from a pet or a commercial breeder, they are still a breeder and should take responsiblity for the puppies they were responsible for bringing into this world. Of course, they may not... which is typical of irresponsible breeding, but I would still give them a call - you may be pleasantly surprised.
If not and you still feel rehoming is the right thing, then do contact breed rescue.
Good luck