Usually the checkin thread isn’t far down the list - it gets a lot of posts so it’s usually near the top. If it’s switched to a new one you’ll find the link to the new one at the bottom of the old one if you need it (though usually you’ll see the new thread near the top of the threads on Talking Sober anyway).
Here’s an example of the link to a newer thread of checkins - swipe down a bit and you’ll see: