I have Roberton's small book in front of me and confirm (again, with Malcolm) Murray on Saltspring's words and notes. "Songs of the Isles : a collection of Island and Highland tunes from various sources," 1950

Roberton (no "s") was fairly well-established a scholar. He definitely claims and copyrights the words in 1937. He gives the tune source as "noted from Dr Peter A. MacLeod and arranged by" himself.

He may be lying but I see other songs in the book attributed to others. I _especially_ note the notes to "Joy of My Heart" on p.18:

"Words by Hugh S Roberton, Gaelic translation by John R Bannerman." Copyright is 1934. This clearly has Bannerman translating Roberton's words into Gaelic, not the other way around.

I suggest that's where the story comes from. All due respect to Bat Goddess. If she says she's seen the news article then I believe it. However, with no date and it not turning up on search, I wonder. It wouldn't be the first ill-researched newspaper article. OTOH, from the reading, perhaps it was just the tune that was played for an actual Mairi - not a song at all.