Besides the loss of what Barks has called "the most complicated drawing I ever did", the damage to the plot line must have angered him. Concerned as he was to balance fantasy with science, Barks would have taken care to explain the crucial detail of the "unmagic stone hammer." In its truncated form, the story gives no explanation. The hammer simply appears and solves everybody's problems.
In a letter to Geoffrey Blum, dated July 15, 1985, Barks tried to reconstruct the missing pieces. "[T]he stone hammer which Uncle Scrooge brings to Vulcan in the second panel of the last page of the story is something that he invented a page earlier while trying to make gold bars himself.... Vulcan's magic one was by then locked up. I dimly remember that Scrooge had a battle with his conscience on whether the world was worth saving, and that he decided to go for the gold, but his slyly-made stone hammer wouldn't deliver the shiny stuff. There must have been something in the business of his developping his stone hammer that led him to later think... that the stone hammer might have reversal qualities, but that important story point has long since vanished into the waste bin along with the half-page splash panel...."
Reading through the story, breaks seem to appear on page 10. This is most noticeable between panels 7 and 8, because the space between them is much wider. Possibly, the vertical black line between the panels (not shown in the Carl Barks Library) is a trace of a cut panel. Mayby this cut art contained a longer meeting between Hercules and the nephews. It could be that more information is given on the stone which Thor uses to offset gravity and maybe some hints are given why some stones on Valhalla have special qualities. On the background of panel 8, a silhouette of the nephews can be seen in which they seem to be puzzled and / or wondering about what Hercules might just have said or showed. (Panel 2, 3 and 4 of published page 11 seem to confirm this.)
The half page Duckburg overview must have been cut from the bottom of published page 13. Panel 5 shows vulcan looking down in fright. This panel looks like it has been cut at the bottom to make room for the caption. A close look at Thor's balloon seems to show that its upper border is added by the editor.
The caption of panel 5 in the bottom half of page 14 could have been added or changed. The composition of this panel was possibly also changed because the left balloon refers to Scrooge who isn't saying anything. This means that the bottom half of page 14 could have been part of more material at this point of the story. If so, maybe it contained a scene of Donald being taken away from the girls and / or Scrooge explaining on that point why he thought of his hammer's reversal qualities? (This is pure speculation.) Living-room panel 6 might have been part of a larger scene in which Donald and the nephews hear the sound coming from outside. It could be that in this deleted part, Louie says: "Another of childhood's cherished illusions reduced to so many nuts and bolts." (a quote mentioned in a letter to Malcolm Willits of December 30, 1960).
Reversing all the gold production on Valhalla is not the only way to re-establish status quo. In theory it can (according to the astronomers explanation) also be done by transferring some of Earth's iron into gold. And that is exactly what Scrooge is working on in published panel 14.7.
According to the astronomer's theory there's no reason at all for the nephews to protest in panel 14.8, as they did on Valhalla before having captured Vulcan and Scrooge. This could mean that panel 14.8 originally showed the conquer of Scrooge on Valhalla, a scene which is not shown in the story as published.
In panel 14.8, especially the left nephew's head seems to be retouched. If this panel originally took place on Valhalla, then it must have showed the nephews wearing their caps. On Earth, in panels 14.6 and 14.7, the nephews are shown without caps. This could mean that panel 14.8 was retouched to make it fit after panels 14.6 and 14.7 by removing the caps from the nephews' heads.
If the story originally contained an ending in which Scrooge was approved to make gold on Earth, but not on Valhalla, then it could very well have seemed a little confusing to a reader who had not focused much on the theorising in the first part of the story. Through-out the story, making gold was the key to all the problems, and then the story ends with Scrooge making gold as a key to the solution. Maybe the editors thought that this was too confusing to be understood easily, especially after cutting two pages out of sixteen, and thus they changed the ending. They had their hands in the story, anyway, and a choice of cut panels to use as new ending.
(A longer, more detailed reconstruction is in preparation.)