This is the Hundred-and-twenty-ninth in my one-book-at-a-time bookshelf.
As a child I never owned a Tintin book. They were a treasure borrowed from the local public library. However their collection of otherwise excellent hardcover editions didn't contain Land of Black Gold. It was mentioned in other books in footnotes, as something that happened was related to an incident from the aforementioned book. I spent many years keeping an eye out for this book. I'm sure you have had a similar experience. It was many many years later that I first read it and it's elusiveness will always give it a certain mystique in my mind.