Wiring problems of the 2001 Mazda Protege

I was at a local restaurant when they announced a Mazda Protege was on fire in the parking lot. Fire department and police were called. Fire was put out and fire department looked to find source of fire. I was told it was electrical. It started in the wiring at the left rear door. The fireman asked what was in the trunk (meaning highpowered amps). I told him everything in the car was original. No added equipment. He said that the only time he had seen a fire in the electrical system like mine was as a result of overload from added speaker/ amps. My Mazda 2001 Protege is being totaled by farmers insurance but they will not have it investigated as to the failure. Mazda has been informed and opened a case but will not do anything without the insurance company's investigation. I am now out a car that should have lasted me ten years or more. I have had no problems with this car until the fire. If the insurance companys refuse to investigate then how do we, the consumer, know when we are in danger. What recourse do I have with either my insurance company or with Mazda.