We lost a dog that way too - complicated by the fact she was deaf and didn't hear the motor bike that hit her.
But our girl wasn't killed. She had a broken leg which was operated on and a plate inserted and antibiotics given and lots of other painful and expensive stuff.
She lasted another sad 10 months until the vet decided to remove the plate, which had loosened screws and was causing infection problems, but then found the bone underneath hadn't healed at all. So she just never woke up. It seemed kinder than removing her leg altogether. She was 16 years old and always in pain.
At least your dog didn't have to go through that.
Very sad for you though.
((((I understand))))
Robyn