December - last edited December
Okay, I had this problem and found this thread. I also have the "Mod that cannot be mentioned". But maybe something has changed, because although I had saved my game after the problem popped up, I was able to fix it. I just went into buy mode for the offending apartments, and when I visited them the next time, everything was back. Not saying it will work for everyone, only for that it worked for me. I also thought that if you could download the same apartments from the gallery and place them, that might fix it too. And I really think that there should be a Maxis contributor that has every original building and family in the game available for download all in one place for anyone who wants them back without having to start a new game and save them all.