I noticed something similar trying to use the GameStop web portal ....no record of my previous purchases. However, when I used the Impulse/Gamestop application, I could see all the games under my account.
You probably still have access if you use the downloader at:
http://www.impulsedriven.com/about
This might be helpful to you or someone else if they have other games via Gamestop. I've also moved to Steam since most games require Steam now. I stopped using GameStop when stuff I ordered directed me to Steam for installation, except in a couple cases where something I wanted was having a great sale at Gamestop.
And yes, Stardock rocks. Their stardock central app should still have record of your old game purchases from their Impulse days.