When he told Noah that he might be of help correcting the misunderstanding that happened between him and Jess. He saw Noah's eyes lit up with hope. Luke's promise of not taking part in Jess's love life flew out of the window.
He knew Jess was devastated by what she heard at the jewelry store. She kept a strong front of being sassy - making a joke of everything in front of other people, heck, she even got them engagement rings.
A part of it was to spite Noah, but it didn't escape from his eyes the small tremors on her hands while she stood straight, spoke clearly and with a dazzling smile on her face. From the way she carried herself in that jewelry store, no one would know what's inside her heart.
But he is her friend. And he knew that she was hurt and in pain.