Well, they are now moved to Dead Organizations sub-forum (which is hidden for the users, but you can acess via http://forum.toribash.com/forumdisplay.php?f=560)
There's no way to actually give these goodbye messages (well, that happened like, three weeks ago, so yeah), but depending on which organization you were part of, you can either search them on the Discord toribash server or in the off-topic board.