I haven't looked for such a court case, but it wouldn't be terribly enlightening anyway. Any case where the question is whether someone "had reason to know" something is going to be rather fact-dependent.
In an enforcement action, the proof that the airman had kidney stones won't be the fact that the airman had pain. The proof the airman had kidney stones will be the CT scan showing the stones or the passed stones. What the FAA will have to prove is not whether the airman had kidney stones, but rather whether the airman had reason to know that he had kidney stones. (Clearly, if there weren't any stones, the airman can't get burned for "having reason to know" he had stones, regardless of whether he was experiencing pain.)
I've never had kidney stones, but from what I understand, the pain is both extremely intense and quite distinctive. If you've had them before, you aren't likely to mistake the pain for something else. If there is evidence that the airman was experiencing that sort of pain, for example because he told someone, then that evidence is probably going to be enough to establish the airman "had reason to know," even if the airman never got a definitive diagnostic test.
The point is that you can't just put your head in the sand to avoid an adverse diagnosis and then claim that you didn't know you had a disqualifying condition. If there was some sort of red flag (e.g., intense and distinctive pain that the airman would have been familiar with from a past episode of the condition) and a reasonable person in that situation would have sought diagnosis or treatment, then the FAA, NTSB, and courts are likely to find that the airman "had reason to know."