Individual posts, or entire discussions, may be removed,
among other reasons,
at the request of the poster,
for possible copyright infringement,
or for inappropriate rudeness.
(Of that last, editing has had the beneficial effect of making me appear both smarter and more polite than I actually am.)
Site Management does not usually even read posts, unless they are Red Flagged for some reason.
Flagged posts are reviewed, and action may, or may not, be taken.
OR, you may have simply lost track of the discussion you recall.
The site's search function works a lot better than it used to,
and Google may retain a cached copy.