Half Life 2 Randomly in Library

[Extra_Random]

I've never played this game before, nor bother to think about buying it yet it has showed up in my library, its fully downloaded but itstead of saying "Play" it says "Purchase" What happened?

[Mark 1.]

You own a game that requiers some textures/data from half life 2, garry's mod for example does that. The game shows up in your library but that's only because you needed data from, well, some game you own needed it. To play it you need to purchase it ofc.

[Extra_Random]

but i've had garrys mod for ages and its only just appeared?

[-Spiffy-]

A similar thing happened to me, just ignore it or purchase it. actually, purchase it. it's a ♥♥♥♥♥♥♥ awesome game.

[jbsob]

That happened to me recently Extra_Random it could be any of the things said above but here is what happened to me. I let my friend sign onto Steam through my computer. Since he owns Half-Life 2 the next time I signed on to Steam it showed up on my Steam because however much data is through the cloud some is put either permanently (till you delete it) or temporarily on your computer. The most likely reason this is happening to you is Steam suggests you purchase it in your library because steam recognizes some data from it or related to it on your computer that recently appeared. There could be other reasons too. Ask Steam Support if you want.