I have never worked on a saturn, but my guess is hidden damage to the engine as a result of the collision.
I have seen similar, seemingly minor accidents do drive train damage. The most common one I saw was to full sized Cherokee and Wagoneers with quadratrac, these vehicles would tqake a minor hit to the front end, and the body repair would be cheap and quick to fix. But, if the body shop wasn't familiar with the drive train, they would miss the cracked transmission case. The drivetrain repair would add another $1800 to the repair bill, usually after the customer got the car back.
I would suspect something like this on the saturn. They are light weight cars, and the transverse engines don't have much crush room around them. Perhaps you could contact a dealership bodyshop that is used to this vehicle and see if there is characteristic engine damage usually found in a collision like yours.