Sims disappearing

[Madame Royale]

I've had a whole family of sims disappear on me before. Like, they moved out of their house but didn't move into another. Luckily there was a sim I could play and have him marry one of the daughters, and then have the whole family move in with them.

So then later on, as the kids are all grown up and moving out/getting married/etc, I play another family waiting for something to happen. I switch back and notice one of the daughters is gone. She moved out but didn't actually go anywhere. I really liked her, and now I can't play her because there's no way to get her into a house. At least, not that I know of.

So, when a sim moves out but doesn't move into another house, where do they go? Is there a way to recover them?  

[Life Hath Immortality]

This can happen in TS3. There is a patch for it now... and sadly there is no way to recover them. D:  

[Menaceman]

When the game was released it was designed so that ANY family or Sim could choose to move out of the town. They may also move back in later on in the game as far as I know.

Later EA patched the game so that any family that has been controlled by the player may NOT move out of the town. Only families that haven't had player intervention. This also came with a warning of not playing too many different families or the game won't be able to remove Sims if the town becomes over populated.

This info also only applies if you have Story Progression enabled. If Story Progression is off then no Sims should leave town at all.  

[pinapplepielady]

There is no way to recover them.

Thats why its a good idea to save your sim to bin whenever they age or you change anything about them.