Odd...
I noticed that my home row of apps looked a little different after a reboot, but couldn't sort out why until just now, when I decided to go to the BB app store and do some window shopping - it was gone?!?
Sounds to me like you accidentally hid the icon. Try Menu>Show All. See if the icon is there, but grayed out. If so, move to it, then Menu>uncheck Hide. Then do Menu>uncheck Show All.
I tried all of that and it was nowhere to be found... so wierd.
Anyway, I just googled it from the browser and re-downloaded it, and it's back where it should be.
These Balckberries definately have ghosts in the machine.