Factorio Forums

I played Factorio today after I updated to 0.17.44 yesterday without problems. After a while I closed the game without any problems.

When I started the game right now via the desktop shortcut, I get the "Install Screen" from Steam because Factorio is not installed anymore.
After reinstalling everything is fine, savegames are found, mods are still there, blueprints are still there.

The only thing I have to do is opt-in to the experimental branch again. I use the 0.17.xx - Latest 0.17 Experimental Option in Steam.

0.17.44 was half an hour old when you made your post, so you certainly did not update to it yesterday. Factorio does not handle updates or installations when using the steam version, so this would be a steam issue.