I am so sorry for your poor little putty cat, I so hope she recovers quickly.
I have no idea how people can just drive off, two of my sisters cat's have been killed on the road and neither time did anyone stop.
I hate to say that I ran over a cat once, I really didn't see it just felt a bump and looked out my rear view mirror and saw it dragging itself off! I got out of my car staright away (leaving it in the middle of the road) to try and get the cat, but I couldn't see it anywhere, it was dark!
I then nearly banged this poor blokes door down, and made him get me a torch and i spent half an hour looking for the poor cat, but to no avail.
I then knocked on everyone's door in the area to say I'd hit a black cat, but don't know who's it was!
I still feel awful about that poor cat, I would have taken it straight to the vet if I'd have found it. How on earth anyone can just leave them to suffer is beyond me!
I'm so glad you've got good neighbours who bothered to do somethign about it.