Had you already looted the chest for that day?
Looking over the recent hotfix, the icon for the chest should disappear now once you have looted for that day.
The Sandworn Chest minimap icon will no longer appear once a player has looted the chest once that day.
Link: https://worldofwarcraft.com/en-us/news/23770463/hotfixes-march-10-2022
Also, here is the link for the Spotlight on GM help: Spotlight on: Game Master Help