World killer bug

I was in minecraft chilling, I went to the nether. I was going to upgrade my axe to ancient debree. I mined some blocks down but didnt notice that the netherrack wasn't dropping. I found some ancient debree, so I mined it. It didn't drop the item (yes I used a diamond pickaxe.). So then I got confused. I left and rejoined only to find things got worse. My entire world was all just sky. All of it eaten. I restarted minecraft but that didn't do a thing. Since this actually happens alot in my worlds, I am reporting it.