I was in the nether and fell to my death, not that far from my portal. When I respawned and went back to the nether, I was in a completely unfamiliar spot, with no nether portal in sight. I restarted the server (It's a dedicated server on server.pro) and I was still there, so I died on purpose and the results were the same except this time there was a nether portal in the unfamiliar spot. I couldn't find my stuff and had to restore a backup.