[SOLVED] Sims got underground

So after I made a party, some guests were leaving but then I saw them going underground and now I don't know how to get them back up.

I already tried to search on the web but I found nothing to my particular case.

Note: Those sims aren't controlled by me, they're just NPCs. Here's an image http://i.imgur.com/wSAnrii.png

I'm not using any expac, and my game is fully updated and I'm running on Windows 7 64bit.

Thanks in advance.