Although I agree that it is very likely the shift tower bolt, I would thoroughly check out the linkage before pulling the trans. See if the linkage has come off at the trans end. See if moving the lever moves the shift tower to make sure that you don't have a broken cable. Most certainly check out the shifter itself. Many have had problems with the ball on the end of the B&M shifter breaking. It is also possible that the cable came loose from the shifter end.
