When a sexual predator abducts a woman in her vehicle, they almost always have to return the vehicle near the scene of the abduction because that is where they left their own car, or less commonly where they live. To abduct a woman and abandon the vehicle in a spot it will will not be readily found would be most unusual because of the perp's own need for transportation and the fact that the vehicle, if it is separate from the kill site, dump site or any other place related to the crime, will no be likely to contain serious forensic evidence or otherwise be useful in solving the crime.
It known facts suggest a likelihood that she had an accident and the car hasn't been found. The short trip to the South Side bar was entirely in developed areas but we don't know where her parents lived or where anyone else who she might have been inclined to visit resided. My best WAG (wild ass guess) is that she is in her car underwater or in deep brush somewhere out of town.