One term that relates to your question is insurable interest. The insured must be related to the subject-matter of the insurance that he/she will benefit from its survival or will suffer from loss or damage to it or may incur liability in respect of it. If you have no insurable interest, you have insurance that is not valid.
Coverage on the other hand relates differently. The car is covered on an auto policy and those drivers are defined inside the policy coverage definitions. Some policies exclude all drivers 14 to 25 years of age unless specifically listed on the policy, while other policies include more specific limitations to those non-listed drivers. Most policies cover all drivers that are not excluded, but given permission to drive the vehicle. There is no blanket answer, so you must refer to your policy declarations and application. Coverage typically follows the car first and then the driver.
Comment Update: Yes, it is possible but not common. Most carriers require the person insuring the vehicle have some insurable interest in the vehicle. However, as of July 2006 CarInsurance.com has a carrier that will allow someone other than the owner of a vehicle insure the vehicle. We also have carriers that will not allow it.
Comment Update: If you cannot locate the insurance information, you should file a police report. The state and police report filing dictates the information disclosure. If none is disclosed, it become a police matter.