Told by a friend of mine (a DL employee) that until your bags are taken off the plane and sent into a baggae claim, DL has no way of tracking your bag along it's route.
The bag is scanned when you check it in, and scanned again when it is offloaded for baggage claim. Bags are no scanned enroute, because of the massive amount of time and cost that would be required to scan all bags at every stop.