Shifter issue / What is this pin?

[csuwatson]

My wife went to put our 2003 Explorer Sport into park the other day and she heard a metallic ping. Now it's tough to get park to engage so you can get the key out unless you pull the shifter all the way up as you take out the keys. I went underneath to see if it was the torx size 30 bolts that were loose and they were fine, but a pin did fall out when I removed the lower cover. It's about one 1 3/8" long and 3/16" in diameter with a small set of cogs on one end. I'll try to post a picture if I can figure that out...

Any idea as to what it is and how to put it back?

Thanks.