Kenny Campbell, a Scottish woodcutter, claimed that he may have carried it up the mountain for a cancer charity in 1971.
But the best-used-before date on a biscuit wrapper found near the piano told a different story.
Members of the John Muir Conservation Trust had stumbled upon the piano about 200 feet from the peak while on a clean-up patrol. The trust now says that the instrument was carried up by a group of movers from Dundee in 1986 who were hoping to raise money for charity.
Mike Clark and his friends had celebrated their achievement 20 years ago with a bottle of whisky and a packet of McVities biscuits, which matched the wrapper found along with the piano.