My only world I converted to experimental gameplay spontaeously disappeared from the world menu. The non-experimental gameplay version was unharmed. I looked in the minecraftworlds folder and the world was still there. I copied the file, turned it into a .mcworld and opened it in the game. It claimed the import was finished successfully but still was not visible in the world list. The new world also appeared in the game files. I even transfered the file to a different PC and tried again but still with no avail.

I am aware that there is already a post for this bug, but it didn't have much information and I wanted to make sure this was seen.