Apple has released a new iOS 8 to the public, this time iOS 8.1.2. The update is available for download over the air on your device or through iTunes. This update is supposed to correct an issue that may have caused ringtones purchased through iTunes to be removed from devices.
You can restore your lost ringtones by going to this link, which redirects you to iTunes. From there, you can recover any of your lost tones. To update to iOS 8.1.2 over the air, go to Settings > General > Software Update, and select Download and Install. The update comes in at around 28MB on the iPhone, and 25MB on the iPad.