isn't there also an uninstaller in the gog folder too? try that instead of the windows add and remove programs.

The game folders no longer existed in the OPs situation, as the drive they (the games) were installed on became corrupt, due to a drive crash...

Edit: But the entries for the games were still listed in the list of installed programs.

You would be suprised. Amongst the offering are save games, and pictures in documents, settings files in documents, install location and in other folders. If the game needs a client then it’s likely that gets installed with its own folders, then if it’s unity it sets up a whole telemetry subfolder system, and unreal has its own set(s) of folders. It’s spirals rapidly.