NLIC.org

Mario Said:

If I put my plates on someone elses car will my insurance cover it?

We Answered:

No, insurance will not cover it. Insurance covers the CAR, not the license plate. Do not even bother trying this -- not worth it.

Angela Said:

does your car insurance on old car cover your new car for 30 days?

We Answered:

Yes and no.
For damages to a purchased vehicle yes it will. An example of this is if you purchased the car and the dealer put dealer plates on it for a week while they waited for you to get plates; during that time your old policy will cover this new vehicle in the event of a collision provided you traded in the old car.
Unfortunately in the situation you are describing the answer is no. it sounds like you had plates registered to you on the car, but had yet to switch the coverage with geico. It does sound like this is the dealer ships error because they should not have released the car with reregistered or new plates to you with out proof of coverage. You can fix this legally because of there error. Call the geico 800 # and explain what happened. Tell them the dealership was supposed to handle the insurance, but in fact had not and still issued you new plates. What geico will do is back date the coverage and give you a proof of coverage letter to bring to court. If you bring that letter to court with you all this will go away.
Good luck.