What about the kid's mother?
The kid was killed in the accident but his mother or Marie as Trevor called her in his imagination was still alive.
Didn't she register a hit and run case on Trevor? It might be that she or anybody else on the street wouldn't have noticed Trevor's license plate number. But still, I think we should have got to see what happened to the mother. What would have happened if Trevor had ever ran into her for real. Trevor would have recognized her as the waitress Marie while she would have claimed that she does not know him. How would the plot have unfolded in case of such an event?