I was out with my 11 year old son on the Downtubes today, when after a steep climb, he suddenly complained that he couldn't shift. It turned out that somehow the cable had popped out of it's receptacle in the shifter, and the barrel end (or whatever kind of end it is) had slipped round into the shifter. I couldn't work out how to get it back out! Pushing the cable back merely jammed the barrel end into a corner, and even with the barrel adjuster removed, it wouldn't come out of the shifter. Any ideas a) how to get it out, b) what type of end it has (in case I have to snip it), and c) how it popped out to begin with?