Why Ipod touch wouldn't turn on normally?

So this morning my alarm from my Ipod wouldn't go off, so I checked it and it was off! Which is weird. So I tried turning it on but it wouldn't work. I actually did the home + power button thing and it worked.

The only difference was that I used the app 'My Alarm Clock' instead of the other 3rd party alarm app. Why would the Ipod crash like this? Would it be an app problem? It's not like it ran out of battery.