The policy provides at the option of the insured, coverage for personal property owned by a person other than a guest or domestic employee while it is in that part of the described location occupied by the insured. Since the friend wasn't there at the time of the loss, he is not a guest, nor a roomer, boarder, tenant. So there is coverage for any property he left with the insured that was kept at the described location. The intent of the coverage is to apply to guests or friends of the insured who have belongings on the property or have left something temporarily with the insured.

I'm looking at the 01 06 policy, and the limit for theft of guns is $2500, even with the endorsement that increases certain limits. The 10% of coverage C is for property of the insured's away from the residence premises which is not the case here. Your policy may be worded differently, but this is pretty standard.

Remember the conditions require prompt notice, in event of theft, the police must be notified, the carrier can also request records/documents substantiating the value of the loss, and can request an examination under oath. The insured as always must cooperate with the carrier. As long as the conditions have been met and the carrier has completed any investigation it feels is warranted, there is coverage.