All of Sudden your WIfi Icon missing / not showing up on Ubuntu 14.04.2LTS operating system.Don't worry follow the steps below to get back the WIFI Icon.
Steps to get Wifi icon on Ubuntu:-
1) Open Dash , Search for "Startup Applications"
2) A new window named "Startup Application Preferences" opens up.From the list check "Indicator Application" and close the window
3) Open the terminal "ctrl+ alt + t"