Please use this thread going forward: Save Game Corruption (Disappearing Lots/Error 800 or 801) | EA Forums - 5037272
This just happened the other day, I had been playing since I downloaded a new pack but a few days later I noticed these symbols on my households and some other generic lots. when I travel to these lots, there are no buildings and my sims can't walk over there. My households will be standing outside where the house would be but the house is missing. I also am seeing a picture of llamas on the "manage worlds" page, some cover households, some cover empty space. I also just realized I am missing the high school.
This issue has been reported before by many others. Here is the main thread on the issue so take a few minutes to read it and me too the first post.
[NEEDS SAVES] Orange Exclamation signs over lots / Houses disappear - Answer HQ
The thread is marked as needing saves so you can send the save to the Sims Team if you choose to by following the directions in this thread:
[INFORMATION] How to Send User Files to The Sims 4 Team - Answer HQ
Basically, those exclamation points and triangles mean that your save is corrupted. Your choices are to revert to an earlier version of the save from before you noticed the issue or start a new save if you don't have an unaffected save.
You might be able to save the lots that haven't been affected and move them to a new game by saving them to your library. Sims too. If you try to save the sims that were on those lots, the chances are high that you can't or the sims will be corrupted. The affected lots are simply gone.
Sorry to be the bearer of bad news.
Hope this helps.
