Q: iOS 9.1 Why did my music files disappear

This just happened to me, too. Sooooo frustrating. I was listening to my music at 8:00 and when I tried again at 12:00 it was gone! This is about the third time it's happened to me, but there's no predicting it. II have only songs I have bought or ripped from my CDs, and Ihave never used Apple Music.

I tried calling support but they're closed.

iPhone 6s. iOS 9.2

This has happened to me twice now since I upgraded to 9.2.  Both times it happened I was listening to music at the time.  I still haven't figured out why it did it.  All I could do was re-sync it to iTunes on my computer and add my music again.  I would like to know how to prevent his from happening again.

I found a partial (only partial) answer to this. I don't know why going offline causes it, but I found out something about the Apple ID. I recently created a new Apple ID to use in the App Store for another country, and, although I was signed into my main Apple ID on iCloud and my device, I forgot to log my second ID out off the App/iTunes Music store. This broke the connection between my music and my main Apple ID, which is the one that knows I have music. That's the mechanics of the problem, but I still have no idea why I have to be logged in. Apple says I don't need to be logged in, as long as the Music store settings on my device are lined up with the right ID. So maybe check to see if you are logged into the iTunes music store. If not, then perhaps the device forgets you have music, and deletes it. Weird that it should work this way, and I know it's not a complete answer, but that's what I know so far.

Clarification: when I wrote that Apple said you don't have to be logged with the right ID I meant that they explained that as long as your ITunes Store has the right ID in its settings you don't actually have to be connected to the Internet, because the app remembers. still seems a bit strange, but there it is.

I had the same issue. This is how I solved it.

Settings - Music - turn off show Apple music then sign out of home sharing at the bottom and then sign back in.

When I went back all my music populated again

It is not known if turning off show apple music was part of the fix so might try just signing out then back in first.

Go to setting, music and turn on iCloud music library. That's how I got all of mine back.

YEs. This worked for me.