you need to get a denial or acceptance from the insurance company, if you can.
then, if they deny, get a reason.
then, sue the owner and the unnamed driver.
Do you have uninsured motorist coverage?
also, you might want to contact the Arizona Department of Transportation Motor vehicle devision. If the insurer denies coverage based on the excluded driver, the owner is guilty of not having the legally required financial liability coverage as required by Arizona law. I have not found the penalties specifically but the DOT website did state that an owner risks suspension of drivers license and vehicle registration.
As well, their insurance company may even drop them for allowing an excluded driver to drive their car.
In other words, the owner of the car has a LOT to lose if the insurance company denies liability. He may reconsider his position once he is aware of all the legal problems he faces if his insurance company denies liability.