If the dog you think is the sire of your puppy is not the sire after all, it doesn't make a heck of a lot of difference if he is Optigen tested or clear by parentage. That is probably just as unlikely as the sire's sire's sire being wrong. The odds of either happening are really small. As in do not cross the street! You could be hit by a truck. Better to spend your energy making sure as possible the people you deal with are trustworthy.

I've heard of it happening with 2 different people and it wasn't a matter of them being untrustworthy. Sometimes oops breedings happen when you have multiple dogs.