Does hibernate in Windows need power?

I put my Lenovo X220 in hibernation, unplugged the power adapter and did not power it back on the whole day. When I went back the next day, I realized it turned off since it didn't have the adapter plugged in, so I pressed the power button and the computer immediately went to the screen where I left it the day before. I'm curious as to what happened. Why did it go directly to the same page where I left the day before when it was not plugged into the power adapter and there was no battery installed as well?
