Round table

So, it should be supplemented with the clause "memory loss situations are interpreted in favor of the questioner."

Yeah. And for club championships, find some "truth serum," or at the very least, it wouldn't hurt to give the particularly forgetful ones a little nudge. But seriously, there's only one option: if you didn't personally clear the guard, you can only proceed if you are ABSOLUTELY sure that your opponent cleared it. Otherwise, you're taking a risk, and in case of a problem, it's a clear tech loss.