Ether’s prophecy was fulfilled. This record does not describe Coriantumr being discovered by the people of Zarahemla (prior to their unification with Mosiah’s Nephites). We learn of that in Omni 1:21.
There are few things in the book of Ether where we can easily know when Moroni quoted his source rather than summarized it. Indeed, for the most part, Moroni summarized. That is not true of the conclusion. At the end, Moroni quotes Ether’s words. Whether the amen was part of the quotation, or added by Moroni is immaterial. For both men, the final word was a testimony to what had been recorded.