Why do threads that were closed 4 years ago reappear as recent post?

While scanning through the "Recent Post" page, I noticed two threads authored by Springer (site owner) that were closed some time ago yet the recent post page indicates that a post was made 37 minutes ago. Why is that?

Here's what I'm talking about;

www.abovetopsecret.com... (last post was made at 9:15 a.m. on 07/02/2009)

www.abovetopsecret.com... (last post was made at 4:34 p.m. on 04/04/ 2012)

Just wondering.

Because they bumped them up so they would be seen again.

The staff can bump a thread without replying in it, allowing them to be seen again at the top of the page. That lets people that didn't read them four years ago reread an important post that they may need to read. It happens every once in awhile.