I'd say it's probably likely that they stole it quickly, and, then, when they got it in the car to look at it, realized that they couldn't do anything with it and threw it out the window. Then someone else ran over it. Perhaps a few cars later, someone decided to remove it from the pavement and throw it over onto the shoulder. Who knows when the footprint happened. It could easily just have been a jogger.

On a related note, thieves are stupid. One day, years ago, a couple of officemates got their cars broken into on the same day (they were in the same lot). One of them had a pull-out unit that wasn't stolen because the thief tried to get it out with a prybar and managed to wedge it in so that it was unremovable. He also stole a bunch of CD cases with no CDs in them (because they were all in the CD changer cartridges, lying right there on the seat). The other friend was driving a Jeep CJ with the plastic doors/roof. I forget what he'd gotten stolen from him, but in order to get to it, the thief sliced through the plastic window. Instead of just unzipping it.