After Rockhopper left, he was not visible through the telescope at the Lighthouse Beacon. Usually, you will be able to see him sailing away from the island after he has left. They have finally fixed this! You can now see Rockhopper again:
It’s good that they fixed this! A problem that they refused to fix was the Club Penguin homepage. Usually, when Rockhopper is currently on the Club Penguin island, his ship appears on the homepage of Club Penguin. But, they unfortunately decided not to add this feature again.