Mr Worried - would/should your original insurers be obliged to inform you that your policy with them had been cancelled?
If so and they failed to do that you may be able to issue a claim against them for the cost to recover your vehicle.
I hope others on here can give you advice on this question - until them I hope I have not given you false hope.
How long a timeframe between your policy being cancelled and the knock on the door?
If not too long, you may be able to prove that you have not driven the vehicle without insurance - if say a month, this could be almost impossible to prove in court.