Invisible Bug!!!

Ok. I was trying to create the 'best' armour and sword etc... and then when I
went into my inventory,I put some armour on, then left. When I went back into my inventory again, I took off one piece of my armour, but then when that item was on my mouse, voila! Most of my player's body disapeared! When i put that piece of armour in my inventory, it persisted. Then i put it back into my armour slot and it went back to normal. I don't know why, but it did.