I love my job. We just had a meeting about things that we didn't know. Not a one of us knew this particular accounting detail. Not even my boss. It just hadn't ever come up. In the end, we discovered that it doesn't even matter to what we're doing.
The point of the meeting? "If you don't know that you don't know something, for heaven's sake, don't TELL someone that you don't know it."
Now if you'll excuse me, I think I need to go ponder the profundity of that logic...