I am headed to southern Indiana first thing tomorrow morning to ride fire roads with a couple of friends - and for assorted reasons had my Jamis upside down at my mechanics advice - and while it was there I played with the shifters. For some odd reason I dropped the chain while it was upside down, but the chain is jammed between the derailleur and back of the crank - and I can't seem to free it

Tips on how I can free it? Moving it by hand doesn't help.