Tom, Elena's father, had told Arthur that the people had broken into their house during the night, taking Elena away.
Arthur asked him if they might be someone from the One Hundred Thunder Academy who was just taking her away to the school, but they dismissed the idea.
"No. The class for her will only start in about two months. They are roaming around the continent recruiting people, so everyone who passes it has to go on their own to the school."
It was a fail, but that did not make Arthur hopeless. The first place he could use to look for clues was the very house he was in.
If someone normal tried to look for clues in there, they would not find it. Even a normal mage could see nothing out of the ordinary.