In 1975, Graham Chapman of Monty Python and Douglas Adams, who hadn't yet written The Hitchhiker's Guide to the Galaxy, wrote a TV show. Out of the Trees was supposed to be a BBC series, but it bombed so badly that only one episode was ever aired. And then they erased the tape.
But almost 30 years later, it was discovered that Chapman himself had recorded the show on home video. For most of us, home video was not a thing in 1976, when the show aired that one time. Chapman had recorded it on a Philips' "Video Cassette Recording" machine, which went obsolete when VHS and Betamax came about. Chapman's partner, David Sherlock, gave it to the National Film Television and Videotape Archive. They set about building a machine that could play the tape, and it took two years. Was the effort worth it? From an archivist's point of view, yes. From an audience's point of view, maybe not so much. From the YouTube page:
As you can see it isn't a lost masterpiece, because it's no longer lost and it never was a masterpiece.