I'd done the same thing the night before, and when i woke up in the morning the computer had auto-powered itself off. However when i started it back up again i found that it had saved the state of everything first, so all my programs were stil running.
This morning however the power was still on, but the screen was black and it was apparently in power saving mode. I tried pressing just about every key on the keyboard and some combinations of keys, and nothing could get it to wake back up again. I finally had to hard reboot it, and of course when it came back on nothing had been saved, so i have no idea if anyone said anything to me after i fell asleep :(