Re: Deleting localthumbcache deletes my game
@MarianneChadwick As a test, please try playing in a clean user folder. Move or rename the Sims 4 folder in Documents > Electronic Arts, open the game to create a new one, create a few households, place them in a new save, quit, delete localthumbcache.package, reload, and let me know what, if anything is missing. You don't need to spend much time on the households, since this is only a test; just put them in clothing you'd recognize so you know whether the items are missing or replaced.
Please do the initial test with no mods, and if everything is intact, add your mods and test again. This is definitely not normal behavior, and the question is why it's happening to you.