it should be simple to find it
ask the witness to try to sketch it or tell it to you how it looks so you can sketch it, and look around the neighborhood. if you live on a main street, they could be miles away. if you live snug away from major streets, then it's more likely that they live near you.
Either:
1. Your cat had intelligence equal to that of a brick and walked out onto the road
or
2. The driver drove straight off the road and into your yard.
I think I'm leaning towards 1.
forget off. You can't expect a cat to see a random black pavement that it's never paid attention to and say "herp that's danger. time to gtf back in house."