Saved games deleted after restarting

@cringeyjesus  You can try searching your hard drive for any stray saves.  Open a File Explorer window, click This PC in the left panel, and enter Slot_* (with the asterisk) in the serch field.  If you do find saves, you can put them back in Documents\Electronic Arts\The Sims 4\saves, and they should show up in-game.  The ones with a .verx on the end are backups, and you'll need to delete the .verx to get them to load, but you don't need to do that unless the non-backup saves don't load.

You can also try looking in OneDrive; it's possible your Sims 4 folder was uploaded at some point.