When Alex ran away, and Clear and Carter and the other survivor (sorry, I don't know his name) look for him, Clear finds Alex near the water. Before she sits down, they show a shot of them from behind. Notice she has a sweater/jacket tied around her waist. But when you see her from the front, there isn't anything there! It is the same color as the jacket she is wearing- she might have been cold, but we didn't see her put the jacket on!