I beg your pardon that I'm vague. I think I remember posting a question several years ago and that it was here on math. I think that the question was about probability and/or some paradox but I don't remember. I'm certain though that I got one comment that was something like
All these years of learning mathematics and I never thought of this....
I want to find what I was writing about. I'm nearly certain that the comment was serious and that the question was received. It was not advanced mathematics. It was maybe a paradox or similar to a paradox.
There is the http://data.stackexchange.com/ but it might not work for such vagueness. It has happened before that I got help finding what I was looking for even though the information is vague.