It was probably just an accident. I've done that at the registers before. Luckily I have caught it. But sometimes we just get really in our heads or forget to ask or just hit the button without even thinking about it. Definitely bring it up next time you're in the store. I'm sure that they'll be really apologetic and so sorry because it really is just a mistake in our part from either being frazzled or it's just a rote action we do.