Personal items usually are not covered under your auto policy, unless you purchase coverage to pay for something like additional customized equipment. Then, it would pay for that customized equipment up to the valued amount.

In some cases, coverage from your homeowners or renter's policy extends to these types of items.

Personal items are not the scope of an auto policy, if insurers were to cover these items them premiums would have to be adjusted to handle the allocated losses.

Comment Update: Sorry it doesn't give you the information you seek, but it usually is not covered under your automobile policy. If you rent instead of own a home or you have a renter's insurance policy then you could file it under your renter's policy.