Happens very regularly here on a current-model iPad mini. Sometimes sound just disappears for no reason I can discern.
Attaching screen recording.
This is happening to us here too, no amount of restarting the game or iPad seems to make it come back. Any time I try to import a custom skin, it's just totally blank/invisible.
Still happens here; iPad mini 4, iOS 13.3, Minecraft 1.14.1.
Thanks - surprising that search didn't turn that up for me when I looked....
Confirmed today - minecraft will run only for the user account under which it was installed, administrator or not.
sudo chmod -R a+w /Applications/Minecraft.app
will fix as expected.