I had a pitchfork on my back for quite a while. I also had it linked to slot #1 of the hotbar. At one point, I found that I could no longer take the pitchfork into my hands, either by using the hotbar, or by manually dragging it. I had not picked up an alternate melee weapon in the interim.
After a server re-start, the pitchfork was no longer displayed in my inventory.