[2023] Save game disappeared

I don't know what could cause that. If you rename those files to something sensible can the game then see them? They should end in .eu4  

A launcher update cannot affect the names or contents of saved game files. Indeed it's hard to see how you could get a Paradox launcher update while playing, as the launcher is unloaded when the game starts!

So far as I know, there is no visibility into the Epic cloud storage, but you could ask them about that.

In general uncorrupting any computer file is like unscrambling an egg (ie impossible), but I suppose it is possible those files only have a minor glitch that some judicious editing could conceivably fix. The good folks over in User Mods probably have the most experience in editing save game files.