Agreed that the amount of knowledge that gets systematized into papers, textbooks, and courses is a small subset of the total knowledge in a field, which is lar

Agreed that the amount of knowledge that gets systematized into papers, textbooks, and courses is a small subset of the total knowledge in a field, which is largely contained in brains. Although regarding your specific example: I believe the current most popular hypothesis about Fermat's Last Theorem is that he did not actually have a proof; it's very likely the proof he thought he had contained errors.