A (found animated short film; 1965)
A is a lost film by Jan Lenica about a writer being tormented by the letter "A". Just when he thinks he has gotten rid of it, a "B" shows up and continues to torture the writer. Unlike most other Jan Lenica films, it was never uploaded anywhere on the Internet, is unavailable for download, or seen on television even in Europe. The film has a tiny Wikipedia page and is mostly forgotten by the general public. Though it is suspected that it might show up on one of Steve Stanchfield's "Thunderbean Animation" DVD sets, no footage from the film has been released or seen; not even a bootleg recording or a production still.
Only 2 prints of the movie are known to even exist, one belonging to Harvard Films, which was once shown at their annual Harvard University Film Festival.
References
http://www.imdb.com/title/tt2111496/?ref_=fn_tt_tt_7 (IMDB page on the short film)
http://en.wikipedia.org/wiki/A_(1965_film) (Wikipedia article on the movie)