> no problem so the pin must have been working free for some time and made it's
> final escape at the end of that flight.  


Pat, glad to hear that you discovered this on the ground. My recommendation is to shorten the hinge pin very slightly (1/4 inch or less) carefully drill a #60 hole at both ends of the hinge and insert a tiny cotter pin or some thin safety wire. I'm sure that you'll hear other recommendations as to how to secure the pin. Pick one of the methods and SECURE IT! It's just too easy to fix and too hazardous not to. ALL of your hinges should be secured in some way.

Bill Harrelson
N5ZQ  320  900 hrs
N6ZQ   IV  0.009%