I don't recall the specifics of the shot, but he's also been known to set up cameras and leave them unmanned to gather footage ... maybe that could account for it? Then again, we only saw around 80 minutes out of his 10 days out there so maybe he did have the opportunity to gather some of that footage personally at some point.

The thing I found interesting about the fire scenes was I was almost positive I saw one of his new knife sheaths - with the included firesteel - hanging from his belt the whole time