If you're running something like smartphone tracker, sprite terminator, nuegpstracker, etc and you try to use one of its features, and it can't get a GPS lock, they have high retry counts set to default... I had it kill the battery on my phone once like that, because in the area of my apartment where my PC is, there is no real open sky view so it never got a GPS lock.

There's lots of things that could have happened, a process could have gotten stuck in a loop and ate up 100% cpu till it died.

I wouldn't worry about it too much, it's easiest to attribute it to being in a low service area. I always keep mine plugged in overnight.