I left my Minecraft world deleted chunks

I left my Minecraft world of 1218 days and then completely restarted Minecraft and when I rejoined 4 chunks of the surrounding area were completely gone. This didn't happen anywhere in the world other than near where I logged off. I'm not sure what to do, I'm what not sure happened. I turned anti-aliasing all the way up before leaving, not sure if that would do anything though. Please help, my chicken died. P.S. I lost ALL my stuff too.