SimonTheBeetle: I uninstalled the program and went back to the folder mentioned above. There were still some residual files and a folder. In that folder, there was an exe. file so I double clicked on it and voilà... the game loaded again! I just uninstalled it, didn't I?!
That shouldn't happen. That means there's a problem with WGT's uninstaller. They need to look into that and fix it.
EDIT: I can confirm the same thing happens here when I uninstall "WGT Launcher" using Control Panel under Windows 10. The name of the file launched when you uninstall is: 2c37965.msi. It leaves behind the "C:\Program Files (x86)\Topgolf" folder and much of its contents.