Can you still see it? I was in the process of taking care of spammers a few minutes ago and maybe you caught it just at the right time. That said, I think there might be a bug or two in the banning/spamming system.
Thanks for reporting @cliffordcooley. Hard to say why, but in the upgrade process I would have assumed that forum would remain hidden/inaccessible but rather it lost the permissions and was set to visible to everyone. It's now fixed.