Several weeks ago I went to get in my car and found the contents of the space under my stereo and the space under the emergency brake handle strewn around the front seat. I didn't find anything missing and assumed a child or vagrant in desperate need of change had taken advantage of my unlocked car. I have started locking my car when it's at home now, but other than that I didn't think too much about it.
I only just realized... those are the two logical places to leave an MP3 player. Not having one, it just didn't occur to me before.