The story about the family member losing a leg is tragic and horrible, but all too common.
Many drivers treat the task of driving like they were sitting at home in an armchair watching TV. They are often inattentive, careless, and cavalier about the safety of others.
I knew of someone who was knocked off his bicycle on a mini round about - clipped by a close passing car. It did not stop. He fell and banged his head. He was wearing a helmet, got up and went home, but was never the same again. He had serious cognitive issues afterwards. He died about three years later at an early age.
Who cares?
No one.
The incident is probably just a line in a police computer somewhere, with 'No Further Action' recorded against it.
Being realistic, unless someone produced dash cam evidence, or had the opportunity to record the registration number, and report it, there is not much anyone could do to track down the driver.
Two motorcyclists I knew have been killed in the last 12 years. Neither was at fault. One was run over by a large SUV on a roundabout. The driver got away with it. The other was killed by a farmer who turned right in front of him from the opposing carriageway, directly into his path. He was an experienced rider who used to volunteer as a safety instructor of newer riders for Durham Police. Much good that did him - sadly.
EVERY motorcyclist can tell you numerous horrible tales of car and other drivers pulling out of side roads into their path. I certainly can. I have three motorbikes. None of them has been out this year yet. Unless you ride slowly on the less busy roads, you are at massive risk. Even then, ridiculous things happen.