I have never bought a dog from a breeder but I have rescued a number of them and have on occasion signed contracts with very specific rules about how I must care for the dog and that if I can not take care of the dog, keep it under my roof, or at any point afford it's vet bills that I must give the dog back to that rescue and that they then keep the dog and the money that I have given them. I understand why they do this and rescuing dogs from a non-profit is very different than buying a puppy from a breeder but without seeing the contract it is really hard to know what they agreed to and exactly what happened or what the "proof" is.
[FONT=Verdana, Arial, Helvetica, sans-serif]I have dealt with [/FONT]Coccidia and a variety of other lovely parasites in recused dogs (they generally always come with something) and it was just a single vet visit followed by one medication. Something seems off with either the health of the dog, the care of the dog, or the vet. It should not have been hundreds of dollars or weeks of illness. Very confusing.