We've confirmed with Major Nelson that the now-aptly named Lost Cities has disappeared from Xbox Live Arcade. Apparently, not too many folks were actually looking for the game, as our inbox holds an overlooked tip about its missingness dating back to March 4th.
The game was published by Sierra last summer, but we presume that those rights transferred over to Activision Blizzard in "The Merger." Microsoft currently has no further details on why the game was pulled, though Major Nelson remarks that it's only the second game to be pulled from the service (the first being Yaris). In case you were wondering, this has nothing to do with poorly performing XBLA titles being delisted from XBLA, that program hasn't yet been implemented -- and likely never will.
[Thanks Josh and Jeremy]