It just happened to me for the first time on my ... iPod touch 6th gen. 128GB iOS 9.0.2.
I had listen on some music offline, than stopped it. When I looked for some messages half an hour later, it's screen stayed black. I thought the battery drained for some reason, begun to charge it, but it didn't started up as it usually does, the screen kept black. Then I reset it (I've seen this post only later) and it was fine, with a nearly full charge (so that's was not the problem). I'm running it since two weeks and that has been my first issue.
I had listen on some music offline, than stopped it. When I looked for some messages half an hour later, it's screen stayed black. I thought the battery drained for some reason, begun to charge it, but it didn't started up as it usually does, the screen kept black. Then I reset it (I've seen this post only later) and it was fine, with a nearly full charge (so that's was not the problem). I'm running it since two weeks and that has been my first issue.