Hello, I use an iPad 2, and recently it got hanged and then afterwards when I opened my iBooks all my ePub files had disappeared. I usually AirDrop them from my mac and when I tried to do that again with the old files, they would just show up and disappear. But the new files seem to be working fine. Is this a bug or are the files still on my iPad? Would be really grateful for any help. Thank You.