Spoiler (click to reveal)
One of the advisor cards says that you may explore an atoll to recover a lost relic. I'm assuming it means a relic that was lost on a ship and you had written lost on it and put it in the storage chest. So the ability cannot be used until you find relics from tombs to begin with.
It started to make sense as I started writing this, but prior to that it was super ambiguous to the difference between a relic or lost relic as it's not particularly standing out on the card and just seemed like flavor description.