References to a play co-written by William Shakespeare titled "Cardenio", which is generally accepted to have been completely lost. There are records of another show, called "Love's Labours Won", but it is unknown if this is a lost play, or simply an alternate title for a show that was later renamed.
To which someone has responded:
It was thought to be an alternate title for Taming of the Shrew, until a fragment turned up that listed them as separate plays. The "lost play" theory is now considered the more likely.
And another person has responded (with an appropriate link):
It was destroyed after witches tried to use it to release their sisters from their prison.
:-) I think I may have squeed like a mad thing. I definitely have a very broad grin on my face just thinking about it!