I just joined in gog galaxy and see that the witcher 3 game was uninstalled...now im installing it again and will see if i have lost all the saved game...omg 45 hours in game

Backup your save games to a thumb drive, or separate hard drive.

Usually Galaxy has "lost" your install location. This has happened to ALL my games more than once while updating Galaxy. (maybe because I install them in c:/games instead of the default location). You can just go into the game in the library choose "More" and then choose "Manage Installation" and point it at the directory it's installed in. If you don't see the game page you can do this on, choose "Configure" from the pulldown menu for the game on the library view page.

I just bought this and had it happen to me today. Well, kick yourself, lol. After you patch the game, the new witcher.exe is located in the x64 folder in its directory. Thus, the shortcuts and paths are wrong. Well, I'm hoping this is the case...as I am reinstalling, but just noticed. What a way to bring up some old news, huh?