This picture is a bit deceiving. He's actually standing next to the stage here, just on the side of it. But the picture when viewed as a whole sort of makes it seem like he is against the wall which contributes to the "lonely" feeling I think. But he isn't against the wall at all, as can be confirmed by examining the arm visible from someone standing behind him quite a bit further back and his water bottle on the stage in front. He's looking off too his left here which is away from the camera's line of sight which again contributes to the apparent mood of the image.
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The resolution really isn't sufficient to tell much about his facial expression here, so personally I don't think you can conclude anything about his emotional state from this image. However, if I had to guess, I'd say he's almost got a very slight smile or sneer here. (the left side of the mouth appears slightly raised) That could be an indicator of disgust or it could be an artifact of this image.
Note also that the fellow in the white jacket to the left of Sam in the image is looking in the same direction. I conclude someone was doing something possibly weird or disgusting over in that direction when this photograph was taken.
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