Today, I took my car to a car wash. I put the key in the cup holder between the front seats. 20 minutes later I got my car back, jumped in, and drove off. A couple of miles down the road I realized that I don't have the key neither in the cup holder nor in my pocket!

I pulled to a side street, stopped, and started to search for the key. I could not find anywhere in the car. Strangely enough, no warning lights were on. I decide to come back to the car wash and get them involved into the search.

As I was making a u-turn to go back, the "key" warning light went on and I've heard a few chimes.

Well, it turns out that the guy who was doing detailing on the exterior put the key under the wiper! It was a relief to find it and I think it could have been worse than that. What if I shut off the engine when I stopped to search for the key? Intuitively, I did not do that.

I don't think I have anybody to blame except myself for not checking where the key is before leaving the car wash. It is not possible technically to detect that the key is not inside the car but rather outside of it, under the windshield wiper. If it were possible I would not get into this trouble today.

Am I correct if I think that there are three sensors and they do triangulation to figure out where in the car the key is located? I suspect, these sensors do not have enough resolution to tell if the key is under the windshield or if it is on the outside.