I'm pretty sure the battle chests are shrink wrapped, or are at least taped shut.. I'd say it's more of a screw up at the packaging factory, rather that GameStop's fault.
What he said, cause I'm pretty sure gamestop can't sell used PC games, what you're thinking of is console games which are the ones without the CDs in them til you purchase them.
Anyways my starcraft battlechest came with the CDs. I registered the cd keys on bnet so I didn't have to keep up with the CDs. You can always buy them online from battlenet, then you get unlimited digital downloads, so its like having a CD you can't lose.