i did something like this a while back. Except it wasnt even my garage. I was waiting for a friend and I was waiting outside in my car in front of his garage. I never put it in park, just sat there with my foot on the break with it in drive (was a noob). After ten minutes, I kinda forgot I never put it in park, and leaned over to get a cd case on the passenger side floor. I wasnt looking up when my car started to roll. I was leaning over and all i hear is crash, thud, crash. I was rolling into their garage door.
To make things worse, I panicked and hit the gas instead of the break, and slammed all the way into the car that was on the inside. To make things even worse than that, it garage was my friend's dad's auto detailing shop, and the car I hit was a client's!
To make things even worse than even worse than the last even worse, I just backed up and went home! I eventually told them a few weeks later. It wasnt really hard for them to figure out it was me. Hmm, my son's friend was waiting outside for my son, when my son goes out to his friend to leave, friend is no longer there, and the garage is smashed in....