The Rooftop Singers (Eric Darling, Bill Svanoe and Lynne Taylor) had the #1 pop hit with "Walk Right In."
They thought it was traditional, which is why they copyrighted it themselves; later, when they learned that Gus Cannon had actually written it, they transferred the copyright over to him. Not sure how the finances were handled; I think he got some kind of lump sum payment for the back royalties he was owed.