After update my netherit sword disappeared. 2nd time. Really frustrating. Just got it back

I just got all my netherit stuff back. And yet a again I had it disappear. I just got it all back. This time thankfully it was just my sword. I dont understand why just the netherit stuff disappears. It’s the hardest stuff to get. How can I prevent this? I’m already saving and exiting. I started taking pictures of items in my chest.