I think someone should stop deleting threads for unknown reasons.
If it was a moderator then I'd say it'd be only fair to get some information about the whats, wheres and whys.
If not, then it could've been only the thread's creator. If you think your thread isn't cool enough anymore, then A) think better before creating threads and/or B) (if it derailed into off-topic) ask a mod to do something before you gonna delete the whole thread. Should the topic itself have been insuffcient, then it surely hadn't reached 3 pages, or mods would have been intervening earlier.
If it was a database error .. well - shh shh shhd - bugger off, you database error you!! (should be fixed now) :P