Robby and Langdon

I was rewatching the locker scene from episode 10 when I first watched it I wonder why Robby searched the locker so convinced he was going to find something I know based on his talk with Langdon he was suspicious but when I watched it again when Langdon is putting in the code to the locker I noticed his jaw tense we don’t see if Robby sees but if he did that would all but confirmed there was definitely something in the locker