The button is there to stop you accidently shifting between certain gears when driving. Ie, you dont want to be doing 70mph on a motorway and accidently hit the shifter and stick the car in reverse.
It also stops the car from being moved out of park for the same reason.
you push the button in laterally and it applies pressure to the top of the gearstick which you cant see because its under the gear knob itself.
If the button has popped out you will need a new gear stick knob. You should be able to get one from a scrap yard or go to a ford parts dealer and they should be able to order one up for you.
If you follow fown the side from the button you will see a tiny hole with a very small hex nut in it.
Remove the nut and pull the knob upwards and it should come off.
You should now be left with just an upright gear stick with a bit at the top you can push down and it will save you having to poke it with a stick.
A quick fix is to cut a "X" in a tennis ball and stick it over the top of the stick just to make it easier to use the gear stick.
It wont win any beauty contests but it will get the job done until you get a replacement knob from somewhere.
Scott Cruz
July 2011