I’m sorry this happened to you @Wave it must be very difficult to have to give up your puppy.
Unfortunately, many pet stores sell puppies that come from puppy mills. These puppy mills need to be shut down as many of the puppies are sick or have long term health issues. Additionally, the conditions at puppy mills are terrible and inhumane for the breeding dogs.
Most reputable pet stores do not sell puppies for this reason. As a community service, reputable pet stores may host adoption events with local animal welfare groups to help with adopting our cats and dogs.