[ros-users] rviz disappearing from my install

I'm running Ubuntu 11.04 on a Lenovo T520 laptop and last used rviz
about two weeks ago. After some initial confusion and troubleshooting I
compared my install to another machine and found that the visualization
package under ros electric install was missing.

I have noticed a few ros electric updates listed during the Ubuntu
Update manager runs, but I don't expect it to remove packages
completely.

Any idea how this could happen?