Revealing mistake: When Cuchillo is about to be shot by Isabelle, you can see the bullet-hole-effect go off too early, due to bad editing. It's exactly in between that scene, when both actors are from the side, and as the scene changes to where Isabelle is seen from the front. (00:34:25)
Revealing mistake: When the predator rips the spine and skull from Stans, in next scene you can see him lying on the ground with his head still attached. (01:12:19)
Revealing mistake: While Isabelle is falling into the hole with spikes the cables holding her are visible.
Answer: Your brother is correct, he picked it up at Noland's hideout.
GalahadFairlight