Who Left This On My Car And Why?

I was parked in the very same spot that my car occupies each day from about 4:15 a.m. until late in the afternoon.   I think the car was centered in between the white lines.  So what was the reason for this note on my windshield on Friday afternoon?   

When I brought it up on the show, Michael and Larry said that it was someone who was upset with me, based on the exclamation point.  If I had done that, I'd prefer to know who and why.

I prefer to think the note was to thank me for some kind deed I had done for someone.   The only problem with that is that I've hardly have ever done anything nice for anyone.

Was it left on my car by mistake and intended for someone else?   Should I have left a note on my own windshield today saying "You're Welcome!"

But whoever you are, you are welcome, or I am so sorry.