If Lambert was hoping to have him react with less fear, well, that isn't happening. Just mentioning that has him startled, turning to try and see, only, obviously, his neck won't turn that far. He does reach back as well, fumbling, finding a bolt.

"No, it's... I thought my back was sore but... what is it? What is it?!"

Cool, now he's panicking. There's something in his back that shouldn't be there and he had no idea.