Minecraft world disappeared unexpectedly; cannot get minecraft to recognise it. (Win 10)

This just happened to me too. One of my experimental gameplay worlds vanished unexpectedly. It is still in my world files, but not visible in the world list. I copied, then compressed the world file, turned into a .mcworld and opened it in Minecraft, but it still didn't appear. I went into the world files and there were two copies.
This also happened to be on Windows 10 1.2.13.

I will post this bug on a separate listing as I'm not sure the information in this comment will be seen.

Cleaning up old tickets: This ticket has not been updated recently (~1 year+) so is being closed as Cannot Reproduce. If you feel this is still a valid issue then please comment, or create a new ticket following the Issue Guidelines.

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