The message is gone. The host apparently opened the site to all without telling me they'd done so (not complaining, of course, except that it would've been good to know so I could remove the message...). Just so ya'll know, I've had to TEMPORARILY remove the reviews so we don't overload the server again. They're still there, just not reachable for the moment. They'll be back as soon as the site is moved.
I'm close to deciding on a new host, so hopefully the move will be soon and we'll be on a server with better resources and won't have to worry about similar outages.