The 1,300-word tale starring the famous detective was found in a collection of short stories written for a local bazaar.
The story is entitled Sherlock Holmes: Discovering the Border Burghs and, by deduction, the Brig Bazaar.
It is believed the story – about Holmes deducing Watson is going on a trip to Selkirk – is the first unseen Holmes story by Doyle since the last was published over 80 years ago.
Mr Elliot said ‘In Selkirk, there was a wooden bridge that was put up some time before it was flooded in 1902.’
‘The town didn’t have the money to replace it so they decided to have a bazaar to replace the bridge in 1904. They had various people to come and do things and just about everyone in the town did something.
‘The Saturday was opened by Sir Arthur Conan Doyle. He had written a wee story about Sherlock Holmes and Watson and this was in the book.
‘He really must have thought enough of the town to come down and take part and contribute a story to the book. It’s a great little story.’