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I think you can reach out to support if you can't find the game and tell them they should add it.

If there is no Bundle / Pack that contains both without anything extra then you have to choose one. Probably the ne that is more worth.
Support wont be able to help either i guess as long as there no such pack in the steam database.
edit: http://store.steampowered.com/sub/48386/ is it the same as that one? if so you could contact support and ask if they could add it to the list.

Not concerning your question:
Du könntest dir mal die Gruppe UL7 anschauen.

Uh. Okay, those are some crazy replies.

To clarify with actual legitimate information:
The first game is free with purchase of the second, which is why you can only post it under the second on Steamgifts.
(Your key is just for the normal store listing of the second game, not for anything special.)

That help? :)