Quote Originally Posted by .noname.silent
actually if you read from past chapters of the manga, zoro had four swords (even though he doesnt use four). he used that sword to get out of the chimney he was stuck in after the first encounter with CP9.
Zoro only has three swords (Wadou Ichimonji[white scabbard], Yubashiri[black scabbard] and Sandai Kitetsu[cursed red scabbard]). The sword he used to get out of the chimney was the Sandai Kitetsu which he dropped when Lucchi threw him out of the room in Iceburg's place. That's why Chopper had it.