It is sad. When I was a kid I watched a car hit my cat. The ass knew that he hit it because he stopped to make sure his car was ok, seen my cat laying on the road and just drove off even though I was in tears and screaming.
You done your best twinkle. Nothing more unfortunetly you can do. At least it is off the road and it is resting now.
I ll tell you a happy story that happened to me last year. I was driving home and a bird flew right into my grill of my truck. I stopped and pulled it out. The poor thing looked in rough shape. I layed it on the passenger seat. It looked like it's wings and neck where broken. I drove it to the closet Vet doctor. As soon as I open the passenger door the darn thing flew away. It was acting hurt all this time........
Anyway, something to make you smile on a rough day.