Invisible Zombie Spawner

I was playing on my friends world on LAN. We were exploring caves and mining, i was getting amazing luck from Zombie Loot. Eventually i realize that the reason why there is so many zombies is because of a spawner somewhere. I go looking for a spawner eventually finding a cave with 3-6 zombies in it, we turn it on peaceful to look for the spawner and disable it but find nothing, i start digging for it thinking its in the walls somewhere but my game crashes (another extremely bad bug) i try reloading the game, it takes roughly 2 mabye 3 minutes but i spawn in, eventually. Tha catch is im instantly dead (another bug) and there is a huge spawner right in front of me where i crashed and was digging. It obviously not being there beforehand. The cave looked totally normal before crash with 0 evidence of a spawner being there other than lots of zombies.

This is a very evil bug that is very hard to re-create. I didnt think at the time to grab a screen shot of what was infront of me after i spawned.

Steps to re-create.
I dont know exactly what to do but this is what i will guess has to be true.
Be on LAN,
Be Mining,
Have a low-moderate amount of lag,
Find an invisible spawner (most likely a few chunks away from spawn point (idk if this would help))
Crash
Rejoin with death to find spawner has become visible.

My brother is on an iPad Mini 2 if that is needed.