bookawoo Sorry for your frustration. I found a bug report that you may want to check out if it sounds like it's your issue. There is a post from EA_Cade in the reoprt (a few messages from the top) where he asks for saves if you don't have and never had mods or cc in the game. Also, if you feel it's your issue please 'up-vote' it. Houses/Lots Disappear | EA Forums - 11901268
Please try a game repair and see if the issue remains.
If you do or did have mods or cc in the game and the first game repair didn't fix it, please try moving your Mods folder to your desktop (save it for reference) & delete the localthumbcache.package file (find them in Documents > Electronic Arts > The Sims 4). Then do another game repair and open the game to see if the issue is gone.