Seniors Discount Caution

As fixed income seniors we watch for discounts when buying. We discovered that Shoppers Drug Mart offers a 20% discount to seniors who shop on Thursdays. We purchased $60 worth of merchandise and to avoid a long line-up went through the self check-out at 1:30 PM. After arriving home my wife noticed that the 20% discount was not applied to the invoice. I went back to Shoppers later that same day at 7:30 PM and was advised that the discount is ONLY applied if you go through the staffed check-out. We assumed that our Shoppers card number would be enough confirmation that we were seniors, but this is not the case.
I asked why they don't post a sign on Thursdays to let seniors know that the discount doesn't apply in the self check-out line, but they had no answer. They then explained that the only way I could get the discount was to return ALL of the merchandise and then repurchase it through the staffed check-out. They further explained that it would need to be done that day, and that everything needed to be in its original packaging and unopened. Of course in the six hours since the merchandise was purchased some of it had been used.
It is my observation that the corporate culture at Shoppers is not designed to ensure a positive end-user experience, and that some of the stores policies are intended to discourage customers from resolving these types of simple issues. I believe that the lost business Shoppers will experience from this policy will be higher than the cost they avoid by making it unnecessarily difficult for seniors to get the advertised discount.