Thank you - who is the Mod and how do I PM her/him?

Been a member since 2006 under a different username and email. Had to create new account because all of a sudden my old account "does not exist," even though I continue to receive updates from subscribed threads. I see that other veteran members had the same problem - but I see no resolution posted here. How can I access my old login? I've found my old posts and profile still listed here, but when I try to login under that old name it, again, says I don't exist. Help...?