Whilst AFKing at a slime farm on a private server, a zombie spawned and killed me. As I was still at the computer desk I saw the death menu appear and quickly quit the game, joined as my daughters account and ran over to get the items (as I was respawned in a bed many blocks away).
There were no items left..yet I saw them on the ground before quitting out It took less than 2 minutes from my characters death to get to where I died, and the only remaining items were what the zombie took after I killed it.
It's especially annoying as I had a mending + infinity bow as the server existed from before that combo was removed from the game.

No item was enchanted with "curse of vanishing"

This has been happening since before 1.11.2 as it's not the first time the private server has despawned items upon death (server has existed since 01/10/2016) but this is the first time it annoyed me enough to post a bug report.

It only seems to be death when a single player is on the server, they quit, and rejoining with a different account that creates this problem...