That was a keychain, Aqua's keyblade is in that room in Castle Oblivion with her armor. Riku allowed Kairi to use the Keyblade at his whim, or some crap like that, as did Roxas did with Oblivion to Riku. According to you, this means Riku's keyblade is connected to Sora, because at the final boss of KH II he wields it for a short amount of time. Also, since this keyblade Kairi borrows was usuable for Aqua due to the memory of Kairi, could this mean Riku obtained a second keyblade during his journey alone due to his connection to Kairi, like how Sora obtains Oblivion and Oathkeeper or could he have obtained a keyblade from someone else? Kairi is not a wielder yet, but will be (most likely).
tidas