Car thieves can 'clone' stolen vehicles. The first you know is when you get a summonse for offences committed in 'your' vehicle.
They steal a vehicle the same model and year as yours, then get a crooked motor dealer to make up plates the same as yours.
They can then use the vehicle and any probs end up on your doorstep.
As to the signwriting: Are the initials in the 'window' supposed to stand for Dean's Cleaning Services'? The 'C' looks more like a 'G'