I'm the one to blame about the placement, but not for the lack of backup. I didn't know where to place the files so I looked up the most authoritative reference I could find, in this case Filesystem Hierarchy Standard 2.3 (http://www.pathname.com/fhs/). Because the game is installed under /opt/ hierarchy, the standard dictates: 5.12. /var/opt : Variable data for /opt Variable data of the packages in /opt must be installed in /var/opt/<subdir>, where <subdir> is the name of the subtree in /opt where the static data from an add-on software package is stored
But for some reason this hierarchy clearly was left out from the backup process.