The small boy looks from John to into the room at the obviously correct deduction and if John needed proof of this, Shinichi just offers up the paper he's mostly, accidentally crumpled. He opens his mouth to say something-to confirm it verbally but once again his mouth fails him and he merely looks back into the apartment.

He's terrible at picking up social cues, but Holmes' tone digs uncomfortably at him-probably because he's still waiting on either an acceptance of rejection and if he can't find his voice soon, it'll more than likely be the latter.