Dulles Airport, just before noon. My daughter and I have dropped off my father in-law. We're sitting in our compact car, waiting for one of the vehicles blocking us to move on. After six minutes, I notice that the engine of the Acura SUV sitting to my left is off. Me: Hmmm. I don't think there's anyone in the car.Daughter: What do you mean?Me: We can't leave because of that Acura... but I don't think there's anyone in it.I wait another minute...