Oh! If you got it through trading there, there's no guarantee a steam key is provided, that's something between you and whoever you traded the key with. Sadly, Groupees allows customers to trade the steam and itch.io keys independently (a principle I am not a fan of because it leads to situation like this one).
You sure can ask them just in case. If they can't help, I'll see if i can find you a key (they take a while to generate now and I don't have one on hand right now).