I wouldn't have noticed if you hadn't pointed it out. I'd just be happy that the guy was on my side.
What does hack me off a bit is when my politeness isn't returned to me, especially by people in retail. Once in a great while I'll even go as far as to say, "Excuse me, I've been saying please and thank you for this entire conversation, and you haven't used either of them once. I'm beginning to think you don't really care about my business."
This results in wide eyes and an apology. Some people just get into a mode and forget to be polite. Oh, and "yup" and "mmm-hmm" are not acceptable substitutes.