If the object??? was part of his vehicle and came loose or broke off, and he has not performed any work or repairs on this object, there is NO liability on his part. File the claim with you insurance company. Make sure you report it as a "airborne" object when it impacted; it would then be classified as a comprehensive claim and possibly subject to a lower deductible. If this object was something the owner tied down or connected and then it came loose, there _might_ be some liability. If a strap he was using to tie down this object failed, the liability might be assigned to the manufacturer of the strap, not the person using it. Not as easy as one would think, is it. I work in insurance. Anyway...good luck.