After discovering Rhythm Thief & the Paris Caper had a few bugs following its release on iOS yesterday, Sega has taken the decision to pull the game until it's fixed. Here's the official statement:
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. 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.