A couple of points:
1. Even though the website says 5-10pm for sightings, they still asked people to be on the lookout for odd behavior the night of 7/18 and 7/19. They may have a solid timeline of when she disappeared based on her texts and electronic data, but no idea what happened afterwards. So they are looking for the husband that was supposed to be home at 7pm for dinner but didn't come in until midnight. The college student who didn't get in until the next morning. Etc.
2. I would not read too much into the "damage to a car" comment. I don't believe they think it was a hit and run. I think they mean if they think MT was last seen/detected in place X, and her body is no where around there, someone had to move her. So someone's car may have damage from a struggle, dents, stains, etc. There is always a lot of forensic evidence in a car when it is involved in an abduction or homicide.