Phil--
Just a guess, since I did it about 30 seconds before I read your post.
While scrolling through the forums, I occasionally forget and click on the right-hand arrow at the bottom of the page. It used to be for the "next" page, but under the new layout it's for the "last" (i.e., oldest) page of any given thread.
Not realizing at first that I've instantly been transported back 4 years, I've clicked on that headline, oh, maybe once a week. Since it's locked, maybe merely clicking on it shoots it to the top of the pile.
I bet I'm not the only one that's done it.
Cheers