I am so sorry to hear that!
This has been happening a lot up here, so much so that this morning on the news they announced that in Tacoma, WA, the police are now driving around in the mornings and if they see an unattended car running in a driveway they will go knock on the door and give a warning - it is now ILLEGAL in that city to leave your car running unattended.
Apparently theives have a heyday this time of year just driving around neighborhoods looking for people warming their cars on cold mornings. The number stolen in that city alone by this method was staggering, I forget exactly but it was in the 100's.
I know your case was a little different, this was a one time deal for you and that makes it all the sadder that it happened to be the day someone was out there to take advantage of it.
Definitely keep us all posted on the situation, we in the Northwest will keep an extra special eye out for things.