I'm not sure about this, but if he got better and was fine after medical care I don't think they would let you take the puppy back. They might reimburse you for the medical bill, but beyond that I think you would probably have to keep him. Also, everything I've ever heard of pet shops I doubt they would even cover the medical bills if it wasn't life threatening or genetic - they know how to word those contracts in such a way that you think you are protected when you really aren't. It really breaks your heart seeing a puppy suffer like that