I have Civilization IV installed on steam and when I play Civilization IV: Warlords it doesn't show in the search of owned game and in recently played items but playing Civilization IV shows up everywhere fine. I'm assuming because civ IV and it's two 'DLC' are all seperate game items but the two 'DLC' have in the store page "Civilization IV®: Warlords requires the Steam version of Sid Meier's Civilization IV to buy." and it doesn't pick up the game properly because of this (or whoever programmed it assumed all related content for the game is classified as propper DLC not a seperate game).

Also I have a total of 447 owned games but only 441 installed and I'm assuming there is another 4 more games similar to this which is why the numbers don't match up even though I've installed everything on this machine.