yeap... it happened to me.
Sorry to be the one to give you the bad news but you might have to go to the stealership to fix that... I ended up there and my experience wasn't so pleasant either.
The little shifter is hollow and the knob attaches to the shifter with a small bolt that should be sticking out of the shifter... it is impossible to screw it back on without dissasembling the console, when they returned the car they had put some scratches on the console...
When I saw what they had done to the car I got so... ejem... 'happy'
and said more than a few words to them...
you know... the kind of words you can't type here
.
They ended up not charging for the job and promising they would replace the damaged parts. The parts are here already, I'm just waiting to have the time to take the car to the shop and have them replaced.