Head over to the Library tab in the Steam window by locating the Library tab at the top of the window, and locate the problematic game in the list of games you own in your library.
Moving these files out and back in should help resolve the problem as it did for many other users who followed the same guide on Steam forums. There are certain files inside your game’s installation folders which manage the games which are currently installed.
Also, if Steam is unable to access this file because of permissions issues, the problem is bound to appear. If these files are broken or missing, the game will appear as uninstalled.
