The Talmud (Bavli, M'gila 6 amud 2) states:
ואמר ר׳ יצחק אם יאמר לך אדם יגעתי ולא מצאתי אל תאמן לא יגעתי ומצאתי אל תאמן יגעתי ומצאתי תאמן
And Rabbi Yitzchak said: If someone tells you 'I toiled and did not find', don't believe [it]; 'I did not toil and I found', don't believe [it]; 'I toiled and found', believe [it].
Well, someone told me today that he hadn't toiled and hadn't found. Should I believe it?
I suspect we can answer as follows: If I should disbelieve that someone has toiled and not found, then obviously it's really hard to not find, so I should certainly disbelieve that he's neither toiled nor found. But I'm not convinced my logic is sound, and I seek other arguments or other evidence.