Not sure how this link proves the point you're trying to make. I can in fact still download all the games that no longer have a page on the Steam store.
There’s at least one game steam pulled from purchase history because it was completely unusable when the servers and auth servers shut down.
Sorry for the late reply. Dungeon Siege 1 had an expansion pack called Legends of Arranna which was sold as a bundle at first on Steam. Sometimes later LoR was removed from everyone's library leaving only the base game. You can download/pirate LoR and apply a steam fix, but as far as I'm aware, you either have to pay or pirate for LoR. The link is "grey" legally AFAICT (pirated but nigh-abandoned)