Minecraft animal pen Bug, (possible)

I can't explain why or how exactly, but one time at the corner of my sheep pen wooden fences had gone missing and half my coloured wool sheep got out, I'm unsure if the server was griefed or if it was a bug which caused it. But a friend of mine is suspect because he was the only one online who knew the whereabouts of my location that night, and he admitted to breaking pens on one of my older worlds, plus after I had discovered it after getting back from doing some fishing for enchantments I found 2 gates were left wide open, one on the sheep pen.

But I rule out fire, because I wasn't in the village at the time so lightning couldn't have done it and none of my pens were built near lava, plus that night I was hundreds of blocks away from my village doing fishing for enchanted books at an old wooden shack another friend had built, so that makes no sense whatsoever. When chunks aren't loaded, nothing is active there.

And when I returned to the village in the savanna biome from fishing none of the remaining fences were on fire. No Creeper crater outside the sheep pen, the dirt blocks were intact and level, and Endermen can only take dirt or sand.

I loaded a backup file to repair the damage. But I assure you the destruction of the sheep pen wasn't my doing and I'm very careful when building stuff like this.

if it turns out that a bug caused the fence posts to disappear, or lag on the server causing fence posts to not register and gates not shutting properly after I placed fence posts after extending the sheep pen recently, then I'd owe my friend an apology for accusing him.

But I'm not holding my breath. Old habits die hard, as they say.
Please investigate this problem, because this has been bugging me for a while now and I'd like to know why it happened.

and if it turned out to be an error which caused it I don't want a friend being accused of something he didn't do.