Minecraft – My friend loses all his items upon disconnect

If you remove the files in the world\players and world\stats folder, the server will forget that they were there. If this is a bukkit server, there is a players folder in each world. Files are named with the ID of the player, so you can delete selectively. To get the ID of a player, open https://api.mojang.com/users/profiles/minecraft/(playername) (substitute (playername) with the actual player name)

First of all, depends on what you are playing on. Single player or multiplayer. If its multiplayer, One of the problems that might be the game failed to load completely or someone else stole it. If it is single player, something might have glitched. I'm not a minecraft expert, but that's my suggestion