The last we hear of Alan in Chapter XIII of Kidnapped is that the land across from where the brig is blown by the wind into a reef is the "worst possible for him ... for it was a land of the Campbells." We don't know the details of what happened to Alan Breck Stewart when the Covenant met her match in the storm because Robert Louis Stevenson takes us along with David to his marooned banishment on the tidal islet of Earraid that lay in sight of Ross of Mull. We only hear about Alan indirectly when David finally is guided toward his escape by two fisherman who realize, between fits of laughter, that David is a ship-wrecked stranger and stranded.
Once David walks across the dry creek bottom at low tide, thanks to the fishermen's gesture-enhanced Gaelic, he finds himself in terrain that seems to be devoid of paths but points himself toward the church spire and chimney fires he had longingly watched from the islet. At last he comes to an old man and a welcoming home and is told in faltering English of shipmates who had survived and of one in particular who had come alone to the same house after reaching shore.
The old man indicated that while the later survivors who had come in a group were dressed in sailors clothes, the lone man wore the clothes of a gentleman and a greatcoat. David recognized Alan's vanity for clothes and knew his friend had survived and was safe even in Campbell country. When the man realized that David "must be the lad with the silver button," he gave him Alan's message to meet Alan in his home land of Torosay. This is all we know of how Alan was saved from the wreck of the Covenant as told in Chapters XIII and XIV.