Chain fell off... (first time)

[aicabsolut]

I think it sounds like it came off the rings (of the crankset) and not the cassette sprockets, since you said it happened with the left shifter. It's not uncommon, though it usually doesn't get really jammed in anywhere. Try pedaling backwards and shifting again in the front. That may free it without getting off the bike. Otherwise, you'll need to get off and pull the chain manually (from the bottom) and place it on the small ring. Then hand pedal to get it engaged.

[Catrin]

Otherwise, you'll need to get off and pull the chain manually (from the bottom) and place it on the small ring. Then hand pedal to get it engaged.

This is what I did, and you are correct that it just came off of the front rings. Once I got it home and turned it upside down I figured out that I needed to work with the chain from the bottom - and will try your suggestion about how to fix it if (when) it happens again. I do think it was from my feeble attempt to shift - the left trigger shifter just takes more to shift it than I expect it to - and of course I am still getting used to it.

I kind of feel like a child looking mournfully out of the window at the snow and ice wondering when it will go away so I can get out on my bike again

[Crankin]

Here is a sure fire trick to getting a dropped chain back on, without getting off of the bike. It has to be done quickly, though.
As soon as you feel like the chain has popped off, put the front gear in the biggest chain ring. It might take a little extra hard push. Keep pedaling and you will feel the chain pop back on.
And, if you have to put the chain back on while you are off the bike, this works, too. Just put it in the big ring and twirl the pedals around to pop it on.

[radicalrye]

I know this thread is kind of old, but if this happens to anyone else it could have to do with the way your derailleurs are set.

One of the 3 little screws you find on them (depending on the make/model) sets how far left or right it will allow the chain to be moved to set it down on the sprocket. If it's set too tight it won't move the chain at all, if it's set too loose it can cause your chain to actually lift beyond the largest or smallest sprockets and cause your chain to get jammed.

If this happens to you and you have no real mechanical skills do yourself a favor and bring it in your LBS to have them properly adjust it.

If you are feeling brave enough you can watch a video on line http://www.bicycletutor.com that can show you how it's done, but that's only if your derailleurs are set the same way.

I personally wouldn't risk it unless i was absolutely sure i was messing with the right screw because once you start playing around with the other adjustments it can be a bit tedious trying to get everything back in order.