In the three hours since your post, I have:
>Repaired the game.
>Once again started with no mods at all with the Premade mod as the single item that isn't the script injector or lot 51, etc.
>Deleted and remade the Sims 4 folder ENTIRELY and did that AGAIN, from the top.
They're still gone and I have no idea why. Not even with no other non-library mods in the mod folder. It is literally there is literally nothing in there but that single folder and things like MCCC and Lot 51.
This was working fine until I updated and had to restart a new save thanks to EA's save-eating garbage. Now with nothing but new saves, it still keeps happening. I don't know what the trigger is, but it only occurs when the premade sims mod is in play.