Over in GQ a thread named “A Math Riddle” is displayed.
When I clicked on it, it contained no post at all. One of those, I thought. But I couldn’t find even a button to post a reply or to contact a moderator.
And then I decided to click on the name of the poster on the GQ page. DoperChic, it reported, is not a registered user and so no posts can be displayed.
So how did the thread even get there?
I’m going to go way, way out on a limb here, and indulge in some really wild speculation, but I think I might posit that maybe - just maybe - there could possibly have been perhaps a glitch in the board software. Unlikely as that is.

Ah, well, I don’t know why you weren’t able to access DoperChic’s profile, but it showed up for me:
http://boards.straightdope.com/sdmb/member.php?u=5405
I did see a “post reply” button in there, but when I tried to use it, I got a “no thread specified” error. When threads get fucked, they get fucked hard.
In a way though, it is a good thing that we can’t post to OP-less threads (of course it would be better if the phenomenon simply didn’t arise), as it prevents all that confusion where the first response (which is usually a witcrack on the theme of missing) is mistaken for a pointless OP.