Backpack stuck under trader POI?

Hey all.

Hubby and I are playing cross-platform. He's on xbox and I'm on pc. His character walked through the door at the trader and glitched through the floor. He had me kill his character so he could respawn but his backpack is underneath the building now and we can't access it. I can't see the backpack icon but he can. Is there a way to get it? He had all his ammo and dukes in there.