One would think that. But saying "I don't recall" when you do in fact recall is lying. For example, if the CFO of United and were asked if ever he ever heard the the CEO of United say "we need more flights to countries like Norway and less flights poophouse countries" and the CFO said "I don't recall", most people would think, "gee, I'd remember if I heard that or not". Many people would also probably think, "gee, I'd probably remember if I'd tried marijuana at all in my life". Sort of like, "do you have any drugs in your car?" "Not that I know of".