Andreas G.

@GoldenHelmet: Can you please give us an update as to when the developers plan to fix this bug? Have they ever looked into the matter?

Hundreds of users have voted for this ticket, but many thousands are affected. It is frustrating to see that Mojang is only collecting bug reports here, but we are not informed about any efforts made to resolve the situation.

Workaround

Never move further away from your village. To go exploring, build a nether portal close to your village and use only this to travel to and forth your village. Once in the nether, travel a long way away from that portal. Place marks along the way or even build a road to ensure you will find your way back. You even can bring a horse to speedily close the distance. Only when you are far away from the first portal, build a second portal to exit the nether. Return to the surface to go exploring, but do not travel too close to your village whilst under the sun.

Always create a backup before you start playing. If the game crashes while you are close to your village, quit the game and restore the latest backup. 

@BenjaminVos — It makes the village update completely pointless

Not only the village update, bees also dissapear when the game crashes.

 @Boidster: — Issue is almost exactly 3 years old now. Definitely a top priority for Mojang. Right after they overhaul cave bats.

I rather believe that Monjang can't just apply a simple fix here but that they have to overhaul and rewrite quite a bit of source code, together with a lot of testing. The bad thing is that they do not keep us informed.

@ThunderWolfs — Is there a way to ever get your mob back?

The only way to get your mob back is to use an older backup of your game with the mob still there.