Could someone help me out?

I don't think it would. Since it must be in his library, so you can't tell until you ask him.

For pre orders, it will still show in the wishlist even if he owns it already.

It won't show up in his game list so you won't know if he owns it either.

Welcome to Steam.

Preorder Borderlands 2 on Steam, it pops up in my libary, but not under Games on my Steamcommunity profile. So you can't check it this way.

If you buy a game you already added to your wishlist before you bought it, it wont disappear on your wishlist :/

But you could just gift it if you want, he wont be able to add it to his library if he already owns it (at least for non-pre-orders), so he can just add it to his inventory.

Ask them, like, really inconspicuously like?

If you don't know them personally, ask one or more of their friends if they know :)

I pre-ordered nd it is in my wishlist it seems, but if you want to check I sent you a friend request on steam.

Thanks you guys. You've all been very helpful.

Cheers c(_)