The one where I actually notice my surroundings

I left work today and headed for the main road. While I was waiting to turn left, I noticed that the car ahead of me had obviously just filled up with gas, because the gas cap was sitting on the trunk, so I honked and gestured wildly to tell the driver that the gas cap was on the trunk. Eventually it occurred to me that I could get out of the car to tell him what was going on, but by that time he had figured it out. He was grateful.