
The mode of inheritance if any of OCD is not known, but it does seem to crop up in some of the retriever breeds and other large fast growing ones more than enough to sugest it is inherited.
As the previous poster said the breeder is unlikley to have been able to predict this happening to one of her puppies, but to say she had never heard of the condition would be rather ignorant of her, as like Hip Dysplasia it is a condition most people in the dog world know about.
What sort of puppy sale agreejment did you sign. In the one I have I explain that the parents are sound and healthy, as is the pu7ppy at time of purcxhase, but as a living creature it's future development cannot be predicted.
There was no call for the breeder to be rude though, and they should certainly note the occurence of this problem in order that it can be taken into account in any future breeding plans. Certainly I would want the mother and any of the siblings retained for breeding x-rayed and checked for freedomn from this condition.