My Sim has disappeared!

[Majick]

In TS2 you can use the cheat "aging off" so that your Sims don't age while you work on their careers and homes.  Once you're ready, you turn "aging on" and they begin to age again.  There is no way to set speed in TS2.  So, if you having aging off and they have a baby, it stays a baby until you turn aging on again, then it'll go to toddler, child and so forth.

As for the unfinished floor, I've never run into this before.  Are you sure it's an actual floor and not just the way the roof is designed?  Sometimes the ceiling designs LOOK like there's a top floor but really it's not.  If there weren't any stairs leading up, it probably wasn't meant to be a second floor.  Or, maybe it was designed to be an "attic" area.