I was following and posted to a thread yesterday in Game Proposials, Input and Advice that has now..gone. No Moved tag, no Deleted tag, and I can't find it anywhere else on the site that I as a generic plebian level user can see. I had to check my browser history to make sure I wasnt losing my marbles.
Its just vanished, like an old oak table.

I've not actually tried, but is it possible for the creator of a thread to delete it and leave no trace?

Are you talking about the war horn wineskin thread? I had been following that one and it disappeared...  Thought I was losing my mind...

I do know the thread was started by a player that was told no by the DM, who was less than pleased the player took it outside the game...   Might be why it was removed...

I felt like I was losing my mind reading that thread, because I agreed with Lissa that the player obviously wanted a drinking horn and not a musical instrument. So it was kinda funny to learn from the DM's post at the end that the player actually did want a multi-purpose horn, for drinking and for blowing (and with a stopper to boot).

The thread was deleted by a Moderator because it was against the site's ToU.  Starting a public forum thread to continue an in-game dispute is not permitted here.