I saved and quit my world in the nether with full diamond enchanted armour and tools, and two ancient debris. There was no lava around me when I quit so there was no way that I could have died. When I came back on the world an hour later all of my stuff was gone and I had no levels, and spawned in at my respawn point, as if I had died. I went back to the place where i left the world, however none of my stuff was there. I also checked in all of my chests but I couldn't find any of my stuff, which I had grinder for over a month for.

overall, I lost

Respiration 3 aqua infinity 1 Unbreaking 3 mending Protection4 diamond helmet

Unbreaking 3 mending protection 4 diamond thorns 3 diamond chestplate

 Unbreaking 3 protection 4 mending diamond leggings

Depth strider 3 feather falling 4 protection 4 Unbreaking 3 mending diamond boots

Looting 3 sharpness 5 Unbreaking 3 mending diamond sword

Fortune 3 Efficiency 5 Unbreaking 3 mending diamond pickaxe

Silk touch 1 Unbreaking 3 mending Efficiency 5 diamond shovel

Efficiency 5 Unbreaking 3 mending diamond axe
2 ancient debris

As well as this, when I logged back on, two parrots that I had just tamed had despawned, and 4 villagers had disappeared, two cartographers and two librarians selling mending and efficiency 5.