I don't quite understand what you are asking.
I am guessing that you are referring to a standard shift, as you did not specify.
What part slips out?
The whole assembly? or the shifter off the nub?
Does this pull out of the floor?
or does the shifter pull off of that nub?
is this the bolt you are missing?
IF all you are missing is that bolt, I would say go to a Junk Yard and get a new one. The "bolt" is tapered. One direction will pull the shifter tight, as seen on this picture above. If you take the nut off, place on the other side, it will pull the "bolt" out to take off the shifter.
Is that answering your question?