Pet shops get their puppies from puppy mills. Puppy mills mass produce puppies for profit only. Quite honestly, you cannot expect to get a healthy dog or good representation of the breed from a pet shop/puppy mill. Any registry other than the AKC is no guarantee that the puppy is even purebred. Pet shops depend on inexperienced buyers like you admit you were to buy on impulse as you said you did.
From Puppy Mill to Pet Shop Friends of Animals | Puppy Mills, Pet Shops, and the AKC Basic Facts Puppy Mills : The Humane Society of the United States