The impression I get from TFA is that this is about "unfinished/unreleased" games more than "lost" games. A "lost" game, film, or work of literature would be one that was published or released, only to disappear again from the historical record.
(To be fair, many of the games listed in the latter two posts seem to be known only via advertisements; it's conceivable that those advertised games might never have existed. But in many cases we know a game existed because we have testimony from people who played it at the time.)
https://en.wikipedia.org/wiki/Lost_literary_work
https://en.wikipedia.org/wiki/Lost_media
Several lost games from the text-adventure world are listed here:
https://www.club.cc.cmu.edu/~ajo/in-search-of-LONG0751/2009-...
https://ascii.textfiles.com/archives/2923 (BlackDragon and Dor Sageth)
https://web.archive.org/web/20140528184628/http://games.wwco... (The PITS)
https://bluerenga.blog/2024/09/02/adventures-1974-1982-lost-...
https://bluerenga.blog/2024/10/27/adventures-1974-1982-lost-...
(To be fair, many of the games listed in the latter two posts seem to be known only via advertisements; it's conceivable that those advertised games might never have existed. But in many cases we know a game existed because we have testimony from people who played it at the time.)