Mysterious Bug Affects Entire World

I have two worlds that were the most successful in MCPE until one day, they disappeared. I know I had plenty of space left for worlds, so it wasn't that. I thought they were gone for good. But then, I scrolled down the list, and they were at the very bottom, with the names taken off! They were put in Creative Mode! I am really confused and I know there is probably no going back, but it seems as if all that time went to waste farming and all of that because I could have done that in Creative in the first place if I wanted. I am grateful the worlds are still there but I would like to help prevent this from happening to me again and to prevent this problem from happening to others, as well. P.S., I dont know if it will show what device after I post this, but when I clicked the device it wont show the name. This occurred on my Kindle Fire.