That coupon clearly says it does not include video game consoles. I'm pretty sure the DS counts as a console. But I bet you'd have complained about that too.
You should have purchased something else for $15, then returned it and exchanged it for the thumb-drive when they came back in-stock...
Just to give my report in case anyone else is searching the forums:
Advance War Dual Strike was $9 (bought)
Polarium was $24 (passed)
Had my bro check the Kmart in a neighboring town and they had
Polarium $3 (bought both of the remaining copies)
True Swing Golf $3.50 (bought 1).