What I expected to happen:

I expected a chunk not disappear upon rejoining world

What I expected to happen :

I expected the chunk to still be there

Steps to reproduce:

no clue

I remember the game freezing when breaking some upside-down stairs (not sure if the stairs matter), then I pressed Esc a couple times, then I pressed E a ton of times, then Enter, then Space, then I tried Ctrl+Alt+Delete a lot. After pressing a lot of keys and waiting for a bit (there was a loading animation the entire time and the game wasn't moving at all) I pressed the off button on the monitor and then the computer. I waited around a couple seconds, turned it back on, waited longer for it to boot up (The computer was probably confused), Launched Minecraft, and I was happy because I could move. But I looked behind me and an entire chunk in my hill base was gone. My cows were running out into the water that somehow was created even though there was never water near the chunk. the hole is exactly 16x16 and water is near the top. My super-smelter, lectern, and stonecutter were removed and a cave connected to my based is split in two. I don't know what could've caused it I just want it fixed somehow if it is possible.

Can I have like a backup of the world or something?