Lenovo K3 Note, deleting every file itself

[AC Question]

At that time, I fell asleep to wait for any of the games (in Drawception to complete). I recharged the phone and I started to realise that all of a sudden that the smartphone itself deleting all my 80s commercial collections without the touch of a finger. This also happens when a soundtrack is not in use and deleting itself. This isn't normal. Do any of you have the same problem? Do you have a solution for this to stop from that happen again? I spent days on collecting commercials.