My lots keep disappearing

Anytime I go into build mode on a lot, everything else disappears, and it's getting wicked annoying. I spent hours working on an apartment and then left to work on a separate apartment, and the one I had been working on was empty. When I tried to reload the save, it looked like the apartment was furnished again; however, when I went into build mode again, everything disappeared. I have no idea what to do, and its infuriating like I can't actually play the game anymore