Sorry for necromancy, but I just have to reply to this because I have had a similar problem with one playable sim that used to be an apartment social townie, and it didn't seem worth it to start a new thread.

I had married her into a family (that lived in a house, not an apartment), and then she moved out on her own when she and her husband broke up. She was in the sim bin when another one of my sims moved into an apartment where townies of her social group would normally live, and multiple clones of her started showing up to move in. They never did, though, and stupidly I deleted her from the sim bin. She didn't show up again after that. Luckily there seemed to only be one of her that Inge's teleporter recognized as being in a household, but it recognized all the clones as being present on the lot.

Is this in any way related to the glitch where neighbors are cloned if they die and are resurrected, or some such nonsense that the official patch was supposed to fix? I have both that and alfixes.