I found this story on Futility Closet's blog here. The story reads:
"You can fool some of the people all of the time.
"Perhaps inspired by Thomas Chatterton, the teenage Samuel William Henry Ireland (1777-1835) “found” an old deed with Shakespeare’s signature.
"His father, a collector, was overjoyed, so Ireland went on finding more Shakespeareana — a promissory note, a declaration of Protestant faith, letters to Anne Hathaway and to Queen Elizabeth, books with notes in the margins and “original” manuscripts for Hamlet and King Lear.
"Amazingly, these were all authenticated by experts of the day. Ireland wasn’t caught until at age 18 he wrote an entire “lost” play, which was mounted at Drury Lane Theatre. As a playwright, he couldn’t match the Bard, and Vortigern and Rowena closed after a single performance on April 2, 1796.
"Sadly, his father took the blame, as no one could believe such a young man could pull off such a forgery. His son fled to France and died in obscurity."
In case you were wondering what the fake play is like, it appears to be a pseudo-Macbeth, but with characters from King Arthur in it. You can read the synopsis here.