Buyer's Remorse

I was treated to Customer Loyalty Rewarding at Indigo Eaton today. To a greater tune than anticipated, and I feel bad. I feel as though I've taken advantage of the customer retention policies of an already strapped store.

I was picking up Hyperion, Fall thereof, and The Dosadi Experiment. They comped me Fall of Hyperion but the actual deal was supposed to be buy-3-get-4.

I want to go back and feel bad, but what's done is done at this point. What would I, or they, even say?