I too would like to offer my condolences.
It is hard to lose any pet for any reason, but more so when it is like this.
I too find it odd they would not stop.
But they may have dealt with this before, as the one time I had a dog run out into the road and I clipped it pretty good I spent quite a bit of time looking for it, as I saw it run off okay, but felt it may have been hurt.
So I called a friend with the police and asked what I should do now, and he said forget it, the dog should not be running free and I had no responsibility to anybody.
Granted he gave me credit for stopping and searching, but told me that was entirely up to me.
But not to lose any sleep over it.
This of course was in a residential neighbourhood as I live within the city limits.
So no excuse for not stopping, but if it has happened before, he may have got the same advice I did.
I just happen to care too much to not stop.