Supposedly, the reference to the fact that “they were never heard of again” (Alma 63:8) only refers to the ship or ships that were lost. In the following verse (Alma 63:9) we are told that “in this year there were many people who went forth into the land northward,” so apparently there was a good consistent communication link between the people in the land northward and the land of Zarahemla.
Geographical [Theory Map]: Alma 63:4,6,7-12 Many People Go to the Land Northward (37th Year)
Geographical [Theory Map]: Alma 63:5,7-9 Hagoth Builds a Ship & Sails Twice--Is Lost (37th Year)