Tricky Seat Knob
 

I recently got a replacement for the drivers headrest knob and snapped it in place. A few days later, it was gone. Last week I found it on the floor under the seat when cleaning the car and put it back in place, this time with a little crazy glue.

It's gone again! Assuming I find it, what's the trick to getting these things to stay in place?

jlc