"What do you mean the vault is empty?!"
"Just that, sir. It's empty."
"There was a half tonne of gold coins in there! Did you see a cart? Any orcs or ogres? A dragon?! It's not like it just got up and walked away!"
Orcs record their deeds through symbolic mutilation, scarring and tattoo. Perhaps creating the medium of skin as art, which humans followed later. Perhaps tattoos remind the elves of orcs and make them angry...