Suddenly logged out of EA app and Sims 4 "uninstalled" itself

@DoktorVintern  The usual fix for the original error is to clear the App's cache:

https://help.ea.com/en-us/help/faq/clear-cache-to-fix-problems-with-your-games/

If that fixes the error but the App still thinks Sims 4 is uninstalled, then the only option is to reinstall it, unfortunately.  Sometimes the App will detect the game's program files and verify them rather than downloading everything fresh, but not always.