Downloaded a .deb file for a game (voxatron) and installed it through the software center. Searching the 'installed' section of the software center for 'voxatron' or 'vox' produces nothing. The software center history is also devoid of any reference to voxatron.
Is there a way to un-install .deb packages downloaded outside of the software center but installed through the software center?
Since Voxatron isn't one of the applications that was hand-picked to be displayed in the Ubuntu Software Center, it is classified as a "technical item" and will be hidden by default.
Try searching for it again, then click "Show technical items" in the lower-left corner:
Even a mainstream web browser can suffer from this opt-out system of classification if it isn't part of Ubuntu's official repositories.
you can type in the terminal
sudo apt-get remove voxatron