Apple has released iOS 8.1.2 to the masses today. The update includes various bug fixes, including the one that caused ringtones that had been purchased via the iTunes Store to disappear form an iOS device.
Apple says users who have had their ringtones disappear from their device can restore them by visiting itunes.com/restore-tones from their iOS devices.
iOS 8.1.2, build number 12B440, is available now as an over-the-air update. GO to “Settings” -> “General” -> “Software Update” on your iOS device to download and install the update.