Did the thing snap "away" from you? Seems like there was a pressure point where the handle bar goes into the stem on the side towards you and fatiguing on the road eventually caused that spot to yield and everything else went along with it.
Do you usually put a lot of pressure on it or hop and land on it? Seems like a freak accident, I'm glad you're ok, must be scary as hell to have the thing come off in your hands.