The more I think about a vehicle being involved, the less likely I think it is.
In either a random hit and run sort of scenario or an abduction scenario where she is dragged into a vehicle, the police probably have that car on camera somewhere. And then wouldn't they be publicizing the make and model of the car or even the license plate? It seems completely improbable to me that a car was involved in some capacity and wasn't caught on camera or seen by someone. If it was caught on camera or seen by someone, I think there would be public appeals to find that car.