Betting the cashier had to PM the price to $9.99 for some stupid reason.
GCU should automatically come off without them doing anything, at least thats how it works for me when I use it in store. Scan my card and discounted price comes up.
I'd go back and complain. $2 is $2.
A while back when BB screwed up the newspaper ad for Dying Light, they couldn't figure out how to "correct" the price and get me the $8 off. (long story, I used a $20 rewards code so it got all screwed up) but instead of $8.. I got $10 due to them not being able to do simple math.
But then again.. it's only $2. Is it worth the time/hassle? up to you.