You're on page 2+ of that forum, aren't you?
Stickies show up on page 1. They're not removed from other pages, so they just flow in as per normal. I was confused by this earlier today, but I can see some value in it if people get to page 2. It's very easy to ignore sticky threads, so this could help ensure they get read if there are some recent updates.
Though really, I forget why I did it this way specifically. Doh!