I think the OP was caught driving the car the day after he bought it, using the 'any other car' option on the insurance for his other car.
This is invalid as soon as he owns the car, so was done for 'driving without insurance'.
The OP is claiming that although he paid for it on the 15th, title didn't change hands until his name was on the logbook, on the 17th. He was caught on the 16th.
It doesn't work like that. Title changed has as soon as you offered a price, it was accepted and you took possession of the car.