I love your strong sensory details--the smell and the sounds of the car, the feel of the twine on Amelia's wrists. (This is something I am personally bad at remembering to describe, or imagine, so my hat is off!)

Your sentence about Simon is a little confusing--from the context, I think it must be something Amelia is thinking, but it sounds more remote, like general narration. Was Amelia the person who couldn't find him?