My son was just logged out of his Minecraft account on his tablet then after logging back in all of his worlds (the ones he's built in) are gone. He can create new ones from the things he's purchased (still available in his account) but all his work with eg xor gates is gone.

I've looked at the file system from my laptop and I can't find anything other than what it shows in app (iow: I can't find the old worlds).

Help?