Alhaitham, coincidentally, always walks out of the house with your house keys, and rarely bothers to return them to you. It could be because of the power trip he gets by only letting you inside when he's home, but he also subconsciously thinks its fun to screw with you. He had stayed out a bit later than usual, and came home to you sitting on the doorstep half asleep, clearly exhausted. His personality makes it hard to feel bad for you, so he keeps his serious expression, but is slightly happy.