Originally Posted by
roger wiegand
OK, I think I understand now. There is a completely separate, semi-linked, PM system that show up on a tab labeled "Visitor Messages" on one's profile page. It contains both the received and sent messages that I was missing. New messages sent there cause an alert in the same "notifications" box at the top of the page, but when you click on the new message notice it takes you to this "visitor message" page rather than to your inbox. There's no way I see to find these "visitor messages" from your Inbox.
Why I'd need or want two independent places for PMs, I have no idea, but they are no longer lost.