Yes, it sounds like a backyard breeder if they didn't do the basic screening tests to guard against hip dysplasia. I say "guard against" because, like someone else point out, joint issues can be exacerbated by foolish things people do like take 4 month old puppies on 3 mile runs, throw balls for them to catch so that they jump off porches onto the driveway to go after the ball dozens of times in a row, etc. You'd be amazed the damage some people can inflict on animals unintentionally. (The same can be said for people who want their 8 year old throwing curve balls and training 15 hours a day to be an Olympic gymnast, both of which result in degeneration/arthritis at a very early age). In no way am I saying the OP did any such thing -- if it's there in puppyhood it's pretty clear it's a congenital condition. But that's why even ethical breeders can't give blanket orthopedic guarantees for conditions that crop up in adulthood.
A conscientious breeder will have done extensive screening for hip dysplasia, actively looking for it and eliminating it. In a breed like Goldens, hip x-rays are absolutely a must-do health screening test for any prospective breeding animals, and have been pretty much ethically mandatory for 10 years or more, which means a conscientious breeder should have hip xray ratings for at least 4-5 generations behind each breeding pair (and a good amount of information on their siblings, as well). As health tests go, it's one of the cheaper ones, especially since you only have to do it once (unlike other tests that need to be repeated annually). It's not foolproof, but it's enough that if done conscientiously, a breeder should definitely be able to prevent recognizable hip dysplasia at such an early age. Just saying "we've never had that problem" isn't enough. A paper trail showing that three quarters of the dogs in the last 5 generations of the dog's pedigree rated Good or Excellent hips, on the other hand, is a sign that the breeder was at least TRYING to watch out for danger in this area.
If it's any consolation to the OP, I once knew a young Golden that a friend adopted from Yankee Golden Retriever Rescue. Shortly after they adopted him they did one hip (the rescue group paid for it), then after he recovered, they did the other. He was a happy, perky pup throughout both surgeries and recoveries, and went on to be a perfectly happy and healthy pet. They were fortunate enough to not have to bear the expense of the surgeryies(and the dog/rescue group was fortunate enough that a loving family was willing to adopt a dog that they KNEW was going to require lots of TLC through several major surgeries).
I can only imagine how horrible you must feel.
