While I was waiting for the train and listening to music on my iPhone 4 (iOS 6.1.3), the music suddenly stopped playing. I then checked the Music app and was surprised to see that it says I don't have any content (songs) on my phone anymore. Did a boot and checked again, everything gone. Settings -> General -> About shows I have 0 songs on my device. I did a bit of googling and didn't find any similar issues. Has this happened to any of you before?