I just got my first Blackberry, a curve 8330 through Verizon.
My Facebook icon has mysteriously disappeared. I have pulled my battery 4 times, unstalled the app and reinstalled it 3 times, checked for hidden icons, all with no success.
Look in the folder called "Community". For some reason Facebook puts it's icon in that folder, don't ask me why, but it does. It creates a new folder called "Community" Something, I believe.
EDIT: Oops, didn't know about the Documents to Go thingy. Sorry...
I don't see a "Community" folder, but Motorcycle Mama got it right... it was in my Documents to Go folder. Not sure how it got there, but it's back on the home page, safe and sound.