Vanilla had had a security hole unfixed since SRK moved to Vanilla. Accounts abandoned before a previous board switch (such as the dead Soy Sauce account) got taken over by the "Unknown" placeholder account since those abandoned accounts no longer existed. The hole is that bots could log in as "Unknown" and edit these abandoned posts to be spam posts.
Last night, SRK was updated and this hole got fixed. All compromised posts apparently were deleted. All non-compromised posts are now written by "System".
Unfortunately, Mandel's Soy Sauce post to start the "Get to know a negro BETTER!" thread in August 2003 was one of the affected posts (and had previously been compromised by a bot last week before I restored it). Since it was marked as compromised, it got deleted in last night's board upgrade... and the entire thread is now evidently unrecoverably gone.