I think people who want to buy a dog should get one from a breeder, not a store. A breeder is more careful about her reputation, a store can just say 'sorry, it was a bad breeder'. But both are counting on the fact that the puppy is so cute, when you discover the problem, you love it too much to exchange it.
My friend paid almost two grand for a Pomeranian puppy, and didn't discover it had asthma until a week later. By then she couldn't part with it.

"Ask and ye shall receive". Sometimes.