I have a very similar issue, however when I selected the special deal "Buried Treasure" I did not attempt to purchase. When I came back after opening some chests with my previously-earned gold, the "Buried Treasure" was missing completely. I have tried opening the app on my iPhone and iPad signed in on my account. I have tried reinstalling and opening though the Gamecenter App. Nothing will make the "Buried Treasure" IAP appear in the store.
My in-game userID is: Nathanamus #2214
Please let me know if I can supply any additional information. Thank you for any help you can provide Aarik!