There are a lot more things to consider than Fanconi when selecting a puppy.
Here are a few things to help you screen breeders.
The things about this pup that would concern me include:
1.) Since the OFA does not recognise "clear by parentage", the sire of the litter should have had a Fanconi DNA test done prior to breeding. I would ask why the owner of the sire did not have the test done, especially since the cost is only $65.
2.) I have no problem whatsoever with an affected being bred to a clear when the sire is the one who is affected and the dam clear. But since there is a possibility that the stress of pregnancy could potentially escalate physical symptoms of Fanconi, I would question why the owner chose to breed this female.
3.) I would ask why neither the sire or dam have had any other health tests done, such as hip x-rays, eye CERFs, etc. I would also ask why so few of their closest ancestors have had any health tests done also. "I have never had a problem with _____." is not an acceptable answer when documentation is not there to back it up.
4.) I would ask to see a copy of the breeder's contract. If they don't use one, why not?
Anyway that's just a few things to think about. Hope you find it helpful.