Aviate
All drivers who operate vehicles airside at LHR (and probably elsewhere) hold a special airside driving pass. In the event of an incident, the police will be called in to establish facts and take statements from those involved, which could lead to them losing their airside driving pass and their job as a consequence. All incidents are treated seriously because of this aspect.
In addition it could be that the airframe/door was damaged such that the luggage could not be easily retrieved.