This is interesting.
Most people believe there was a treasure, but it's not there now.
If we accept that as the way it really is, then the explanation for the events on OI must accommodate this truth - finding the story behind the legend, as it were.
One explanation that accounts for this new fact stems from two episodes of OI.
1.When the McGinnis sisters were on, they said the family lore was that the original three recovered 3 chests.
2. There was a visit to the man who inherited? Captain Anderson's (a lot owner on OI) chest to see if there was any useful information in his personal papers. The owner made a big deal of presenting a 4 key keyring, one of which opened the chest. Where did the other 3 go?
I don't think COOI scripted that connection since it would cast doubt that the treasure is there, which would tank the reason for the show to exist.