This is the second time I find the weapon case forgotten in the Kurohana ship. If you take a loot at the map, you can notice that there's no hunt squad or even most wanted contracts which usually indicates that there's no more players in the game, yet the weapon case remained in the ship.
I took my chances and went inside the ship, what do you know? Dead Kui Ji still had the case on him. I just picked it up and headed towards the final extract, I was very calm while waiting for the helicopter to take off since no one was gonna go after me. It was just me and Number 2.