Stim == well before 1979. Auntie Peggy would tell this story in the 40s. But not really a related story. Such disappearances as that you relate quite often get told of. But in Auntie Peggy's story, the point is that he had planned it to leave his wife & perhaps go off as arranged with a mistress, or some such.

The story of the MP, Stonehouse, who (unsuccessfully) faked his drowning to vanish & escape arrest is nearer; but not that near.

Actually, Lighter, Holmes did eventually solve that mystery, in one of the follow-up stories from the 1950s by Adrian Conan Doyle [son of Arthur] & John Dickson Carr, published as The Exploits of Sherlock Holmes (1954), which took up & expanded some of Watson's throwaway refs from the originals.

≈M≈