This happened to me in the past. I found out until I got a car accident. It is other party's fault. Other insurance paid me lost. However, I sued my insurance for canceled my insurance.
Since the car belongs to you. And the car insurance is attached to the car. That is belongs to you also. Your ex didn't have any right to cancel it. I just told judge about this. And then insurance asked for a break. So we could discuss this. And then they gave me the offer, $1000 for canceled my insurance.