As "dl" guessed the plot in the previous post was written by Carl Barks. And since it's labelled "Idea for future story, Scrooge O/S." I assume it's from the early fifties.
(There were only three Uncle Scrooge O/S.) Barks from his peak period in other words.
This plot is not in any of the library books. And as a bonus for todays post you'll get a photo of Barks first draft. Notice that there are differences. Click to enlarge.