Erebus turned up 100 miles away from where she was officially supposed to have been abandoned- which requires explanation. The most plausible theory is that survivors reoccupied her and sailed her south before abandoning her again and disappearing into the snowy wastes- thereby- though they may not have known it- navigating the North West Passage and successfully completing the mission.
The archaeologists found the wreck thanks to Inuit oral tradition. The Inuit turn out to have been right about everything- including the cannibalism that some of the lost sailors were reduced to (archaeologists have found cut marks on human bone at one of the camp sites,) Dickens was one of those who bloviated about this when the information first came through, accusing the Inuit of being primitive idiots incapable of appreciating the mettle of true-hearted British tars. The word "blubbery" occurs in his article. I adore Dickens this side of idolatry but he was capable of being a right plonker at times. One can imagine him- in a later incarnation- writing columns for the Mail.