Hey it's DoctorWhu11.
Recently on some single player worlds and some privately owned servers, I haven't been able to hold an item. I would put it in my hot bar, the scroll over to it, and it would disappear. Please help me. Thanks.
They are items that can be used only by certain players.
This means that you gave yourself an item that is player locked such as John's black box and it vanished from your inventory what you need to do is go to gm 1, and hold shift and double click the pink x in your inventory to the right of the hot bar. It will completely clear your inventory. That will solve the issue.