I don't want to sound harsh here Third Mate, but you pretty much accused this player of being a pirate with the 'doesn't add up' remark and your question as to where/how he bought it.
And that's after not one, but two admins already were looking into it. I don't know who the 'us' is your refer to, but I am pretty sure you dont really have the means to offer any help with this kind of license key issue, certainly not if you don't even understand what his problem is and start questioning a customers' honesty because of that.
If you feel the urge to post something helpful, that's cool.. and more power to it! We always appreciate that a lot. And if you get it wrong or not quite right, that is no problem either of course, help is appreciated at all times and no one knows everything.. but please don't go posting suspicious remarks like that. It's really not cool, mate.
@SAM 68, I trust you received my pm the other day? Steam is still the best - and maybe only - bet in getting this sorted, as the keys they distribute for the game and the DLC's that you own, are different from the Vstep ones. Even if we'd give you new Vstep ones, those would not work.
Again, sorry that we can't be of more help from this side, but by now I should think the support there at Steam would have sent you an answer. But if they still have not, could you please drop me a link to your steam profile in a pm to me, for reference, and maybe paste in the text of your original support ticket? Then we'll see if we can light a fire under it and contact them for you.
Regards,
Fred