Sometimes mobs disappear instantly. Like Cows etc...
Comments 4
Cleaning up old tickets: This ticket had been set to 'Awaiting Response', but has not received a response from the reporter (~3 months+) so is being closed as Incomplete. If you feel this is still a valid issue then please comment, or create a new ticket following the Issue Guidelines which includes steps to reproduce the problem.
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Mobs despawn when player moves away from them. To make them permanent you need to interact with them, i.e. feed the cow.