Stuck front derailleur On a ride recently my front derailleur seems to have gotten jammed. The levers wouldn't index and the derailleur itself wouldn't budge. After continuing the ride for a bit, the problem went away on its own. What could have caused this? And how can it be fixed more quickly in the future?

It is a Shimano Deore derailleur, and it was stuck in the smallest chainring position. The bike is new with less than 50 miles on it.
Often while mountain biking a twig or rock will get stuck between the swing arms on your front derailleur. This effectively locks the derailleur in place until the rock/twig works itself out. 

If it happens again, stop and examine the derailleur. Generally you can't see the obstruction while you're riding.