I was playing on zombies and i died, on the lobby waiting for someone to revive me my wifi started to fail or something and then i disconnected and when i tried to join again all my inventory was like in that zombies game, with a copper sword and crimson armor and i had the surprise that even the singleplayer profile was like that
I’m afraid that there isn’t much to do as far as I know. The same thing happened to me a while back, and I didn’t ever find a solution to the issue.
For all I know though, the mods might be able to look through logs or something and find your inventory, allowing you to get it back.
If not, I would recommend just grabbing all the items you remember having from the items area of the server. It won’t be perfect, but it would be as close as you get to an actual solution.