Chestplate Problem

[Idthename]

I just go to boss world and com back after fighting boss and the chestplate turn 0 and when i take it off it disappear WHY IS THIS HAPPENING?!

 

[Roguemaths]

Yeah same problem with me too. Later I found out if you grind mobs(in the overworld) wearing Thorns armor, your armor takes durability damage and then this happens. So if you grinded mobs then that's the reason otherwise don't know.