Hi Mark,
I'm andy - William's brother, and I host this site on one of my servers.
Been chatting to John (Tolak) - who pointed me at this, and certainly it wasn't intentionally deleted, and there's nothing to indicate why its disappeared - as far as I know there's no autodelete configured, and there's certainly plenty of space on disk for the database to expand into!
I've been trawling through backups, and am going to try and restore this topic from there.
This may take some time, as I want to test it, to be sure it doesn't affect the rest of the site.
So please bear with me
thanks
Andy