When going through a nether portal, from the nether to the over world, I got stuck on the loading screen and, after a short period of time, I started hearing the sound of a player taking damage. another player in the world (we were playing on the same screen in co-op mode on a Nintendo Switch) saw a death message that said I had suffocated in a wall. After the other player had done a quick search for my gear and inventory in the over world and nether, they logged off, leaving me alone, still stuck on the loading screen. I restarted Minecraft (without saving because I couldn’t do anything), and I was at the last bed I had slept in without any of my stuff. I looked everywhere in the over world and nether where I had died, but my items had vanished. This only happened once, and the portal worked fine while the other player and I were searching for my gear. There was some lava under the portal in the nether and a bit of fire. The portal in the over world was in a room with a top slab floor and nothing dug out under the slabs.

Update:

I went to the coords of the nether portal in the over world, and all my items were there. Thanks to GoldenHelmet for the help. The seed is 1823182294 the nether portal coords are -2048, 79, 265 in the over world, and -255, 33, 34 in the nether. I found my stuff at around -255, ?, 34 in the over world, I don’t remember the y coord, but it was at ground level. Parts of the world were generated in 1.15, and new chunks have been loaded with every new update. Where the portal is in the nether, and where I found my stuff were generated in 1.15, where the portal is in the over world was generated in 1.17. Thanks again for the help GoldenHelmet.