phone just turned off

I was using the map feature and when i looked down at it, it had the countdown timer thing, and then it turned black. Now it won't turn on or i don't know what. It didn't give me a low battery warning, I need to know how to turn it on or what i did to make it turn off like this! I'm stranded without my phone. I rely on the map to get me to place, I just moved and i have no idea how to get around!!! someone help me please..