Buried treasures missing

I used a buried treasure map to locate buried treasure, but the chest isn't there. I dug away half the island, from the top to the bottom of the ocean, in a huge radius.

My world was created before the Aquatic release. I copied my world and was able to find the chest easily. But it's not there in my original world.

My seed is 5355231335720978802 and the treasure is supposedly around 2,457/-2,470.