If that happens again, try lsusb to see if your blackberry is in list. Sometimes it doesn't appear. Such is linux life. :P
If it doesn't appear, just click desktop then unplug and wait a short time, then plug your blackberry in again. Make sure it's unlocked at that time, and not in lock screen.
"There is no reason anyone would want a computer in their home."
- Ken Olson, 1977
( And we now wear them! Blackberries are computers too! )