Yoou sure you did not turn your truck around on that door?Someone drew a big pair of boobies in the grime on the back of my truck one time. Problem is, that grime is gravel road dust so they might as well have scratched it into the paint with a piece of sandpaper. Even after it got washed the boobies were still clearly visible and it was over a year before the door finally got repainted.
I'll have to see if I can find the article but there was a TV special on a guy that did "paintings" on the back of car windows.That's pretty good. If he did that well with just his finger in some dirt. He should do those 3D pictures in the streets on the side for extra money.
http://www.hongkiat.com/blog/absolutely-stunning-3d-street-art-paintings/
I'm wondering if the trailer possibly came in from Seattle because if you look closely at the bottom right, I believe it's a city skyline and what I think is called the "Space Needle "next to it.