Does homeowners cover someone elses property?

Most policies would be written to restore the policy holder from damage that occurs on the insured property to items that are kept on the property. If you were responsible for the other person's property (you were borrowing it) and you could document the loss, you could argue that you should be made whole. You could, under most policies, seek replacement cost for property damage that was caused by your actions on your property (you drop a bucket of paint off a ladder onto your buddy's car parked in your driveway). This, on some policies, is extended to damage caused by you or occupants of the insured property while riding a bicycle, covered under the policy, off your property. Likewise, damage caused by your dog that gets loose may be covered.

There is no way to give a tighter answer than "Maybe". You need to discuss the specific incident with your homeowners' claim adjuster. You may need to have notified the insurance company of certain things beforehand. It is unlikely that your homeowners' policy will pay for a 'big-ticket' item unless you had itemized it beforehand e.g., you are storing your buddy's car in your garage and the garage burns...if you didn't notify that you were storing the car, you may be on the hook for it.