Missed out on activate rewards because "supplies" ran out

This ever happen to anyone else? My receipt was approved for that spend $40 get $10 on xyxal/allegra/etc promotion and I received an email that it was approved and to activate my reward. I did, only it wouldn't go through and now I'm being told that the promotion was "exhausted" because per the terms it was "while supplies last." I'm more than a bit pissy about this because I'm feeling like the freaking website shouldn't be up and taking receipts if there are no "supplies" left!!

I imagine there's nothing I can do but I needed to vent. And maybe have someone commiserate lol.