Yesterday I updated my survival world to 1.16 and like everyone, started exploring the nether. I got some netherite, gold and blocks like basalt, etc. I made my equipment of netherite, and the rest of items (gold, netherite, basalt, distorted mushroom, etc) got stored in a chest. Then some minutes later I left and later I joined. I went to the chest where everything was stored... but there was nothing! Then I thought it would be a punctual bug that later won't happen, so I went again to the nether to get some gold (I need a lot and for the moment I don't have a gold farm) so I again stored the things I collected in a chest. Then I continued playing, left, and when I joined, the things were gone again.... I have this video as proof.

https://youtu.be/5RoE7l3evAs

PD: I also tried if it happens on 1.16.1, and yes, it still happens