How does Jeeves explain being in possession of Mrs. Trotter's necklace?

After Seppings reveals that he found Mrs. Trotter's necklace in Jeeves' room, Jeeves is called downstairs to explain himself. Jeeves says that he found the necklace in the hallway, and had taken it into his room assuming that it belonged to one of the maids because it was clearly not a real pearl necklace.