Firstly are you sure it is a Cocker, and not a Cavalier King Charles Spaniel, as the condition is to my knowledge not prevalent in Cockers. Secondly they should definitely contact the breeder, whether or not they want to know is another matter, but any reputable breeder would have tested the parents before breeding. Until people learn to only buy puppies from health tested parents, be it heart conditions, eyes, hips or any of the other conditions dogs can suffer from then people will still produce them without testing to make as much money as possible. If I was spending good money on a puppy (pedigree or crossbreed) I would want to make sure the parents had been tested for every available test for that breed. Might pay a bit more but probably cost less in the long run with vets bills so high these days. Trouble is, all pedigree dog breeders get blamed when something goes wrong, but there is enough information out there now and people have to take responsibility for what they buy. Puppy farmers dont test, and many people who advertise puppies on internet sites or in free ad papers dont bother either. Go through a breed club to find a reputable breeder who does all they can to ensure a healthy puppy.