"Try to remember." Rewen urged. 'There are two possibilities. One, she really did forget it randomly. Two, she forgot it and it's a plot element. If we go by observations, it could be concluded that she isn't the kind of person who is too clumsy… or maybe, she did forget something randomly. However, how could I dismiss the possibility of it being a plot element?'
It had to be said that he had grown significantly more cautious than he was before. A major part of it has to do with his previous mistake - dragging his cousin Denny into his own mess. It was a mistake he regrets to this day, and it happened because he was careless and overconfident. He had gotten too absorbed in his own little hypothesis where nothing would go wrong. By the time he had finally realized it, it was too late.