Network manager indicator missing

Motivated by this post on Ubuntuforums.org, I have found a solution to my issue in two steps.

1. Purge and reinstall network-manager-gnome:

   sudo apt-get purge network-manager-gnome && sudo apt-get install network-manager-gnome
   

2. Add nm-applet to the Startup Applications (which may be found by entering "Startup Applications" in the Dash and setting the path to /usr/bin/nm-applet).

   I verified that the latter step was necessary, as the indicator did not appear after login without this addition of nm-applet to the Startup Applications.

if everything else fails,use this

sudo apt-get install indicator-applet-complete

quick restart and you should see it on the panel again