Earlier in the day, when we arrived home from a busy morning, I had rested my mug on the roof of our car, to unload my daughter in our driveway. Later in the day, when I had to do errands, I drove 15 minutes, making five turns before pulling into this parking spot, climbing out of the car, only to see my mug still sitting on the roof of the car.
I'm sure there is a scientific explanation for this, but I like to think I am one smooth driver.
I'm pretty sure when I learned how to drive, you're supposed to do some sort of spot check of the vehicle before you enter it.
(Also, yes, I am aware that this could have been extremely dangerous had it shot off the car and hit someone, and that I should, in fact, purchase a proper travel mug for coffee on the go.)