There was a small plastic cap covering this hole on the door frame (drivers side). I accidentally pushed it through. What is the correct part that goes here, and what do I need to remove to retrieve the fallen piece?

When you open the drivers side door, towards the back...



[attachment=56806::]

One of these?



[attachment=56807::]

 

I think it is this part under Grommet section:
91657-SP0-000 011 009 SEAL C, DOOR PANEL HOLE (25MM)

Not sure how to retrieve the fallen pc.