I would guess that the insurer was preparing to write it off as a Class D before it was recovered, then forgot to take it off the register when it was recovered and repaired. So you need to get your insurer to undo its mistake with the threat of legal action for the damages it has caused to you by libelling your car as a write off. The insurer can't have it both ways. Either it pays you the write off value of the car and takes the car off your hands, or it compensates you for your loss as a result of its negligence.