UPDATE: Rhythm Thief's iOS launch has turned out to be short-lived - publisher Sega has pulled the game from the App Store after discovering an "unexpected problem".
"An unexpected problem has been discovered in the version of Rhythm Thief that was available yesterday on the Apple App Store, so we have removed it temporarily from the store as we work on a fix," a spokesperson explained. "Our development team is hard at work to update the game and it will be back online very soon.
"Anyone who has purchased the game already will be able to play it as soon as it is back. We will keep you updated and we thank you in advance for your continued patience."