During the final battle scene, Merry & Pippin lead a group of orcs away from Frodo. They are then surrounded, and it shows several orcs charging towards them. The camera then cuts to Boromir running towards them. Nowhere on him is the Horn of Gondor. The camera cuts back to Merry & Pippin, then back to Boromir running again. This time, the Horn is suddenly visible hanging in front of him by a shoulder strap.