@kahrhen It sounds like the issue may have been that Sims 4 started reading a different user folder, first when your original saves disappeared and then again when your new ones disappeared and the old ones showed up again. This can be due to OneDrive issues, but that's not the only cause. In any case, step one is to figure out exactly which folder is being used. Here's how:
https://sims4.crinrict.com/eng/2018/07/how-to-find-your-user-folder/
The part of this guide that explains how to find your missing saves is definitely relevant; whether the other parts are depends on whether OneDrive is involved. If you don't have any luck searching for your saves in File Explorer, you can try using Everything, from VoidTools, instead. It's a more efficient search tool and should turn up any saves left on your computer. Hopefully you find some, or they're on onedrive.com (My Files or the Recycle Bin), because otherwise, there's really nowhere else to look, unfortunately.
