Ah. We have the Xbox version. For some reason I can't keep my attention on computer games (and my computer is not awesome enough to handle the graphics anyway). The cover shows P-body jumping between portals. Which is... just not nearly as epic as GLaDOS glaring at you in the ruins of her room, for example.

The older backstory would be fun, and would be something I could sort of see them exploring in Portal 3? I think people really wanted to see Chell make it out of that place, though, and I can't say I blame them. Poor Chell.