Apple has officially released iOS 8.1.2 to the public, a minor maintenance release that notes “bug fixes” as well as addressing a problem with missing ringtones previously purchased through the iTunes Store.
The ringtone issue has been noted in an Apple Support article, which provides instructions for either restoring missing tones by syncing with the associated iTunes library containing those tones, or visiting http://itunes.com/restore-tones from Safari on an affected iOS device after updating.
iOS 8.1.2 is available as an over-the-air update or by updating via iTunes on a Mac or PC.