Comment by rhamzeh

AFAIK, even if the developer removes a game from Steam, if you bought it (or rather, a license for it), it remains in your account.

E.g. I have Lord of the Rings: War in the North that is no longer available anywhere, yet I can still download install and play it on my devices through Steam (even on Linux, which it was not intended for)

That of course doesn't help if the game does not have an offline component, e.g. I also still have League of Legends in my Steam account, but that is unusable because the Riot servers don't allow updating/connecting from it.