Please use this thread going forward: Save Game Corruption (Disappearing Lots/Error 800 or 801) | EA Forums - 5037272
I'm not getting an error code but I am getting at least one lot that appears fine in the overworld and then changes to an empty lot when I try to load or edit it. I'm afraid to make any new saves on this file in case it becomes permanent, since I don't have the lot backed up in my gallery and I spent a lot of time building it.
You should often make copies of the save files and put them to a different folder so if anything happens you can go back to an old version and find your lost build. Also upload every build you made to the library so you can access it from different save files anytime. i also recommend copying tray files to a different folder.
