Cops can easily call any insurance company and verify exactly whos on the policy. Primary and secondary driver(s). No conspiracy theories there.
You giving us the entire story?..
Cops obviously have first and foremost some interest in your car… either it was seen in or around an area where a crime was commited could be HTA offense or criminal, or could simply match a description given or found on a video tape. If you are clean you have nothing to worry about. If they can properly identify and match the car to yours… they WILL be speaking to you next.
For now the only bit of information they wanted was to confirm the driver/car and to gather any information they can… that is before they will approach you (if they do) it’s a pretty standard police investigation procedure.