The “we” in this verse refers to Mormon and his time. For Mormon, there was no record of any further return, nor any indication in the subsequent years of what happened. Apparently, these ships planned to return since their failure to do so led to the assumption that its passengers and crew “were drowned in the depths of the sea.”
Another possibility, of course, is that, whatever their original plans, they made landfall to the north and either merged with the people in that area or were killed by them.