Anyone else every done this?

So, in an effort to do my part for the world, I have been using my reusable grocery bags on a regular basis. I love it. They are strong, hold a lot of food, etc. Well, today, as I was paying for just a few groceries, I noticed a package of batteries that the bagger was placing in the bag. These were small little "N" batteries. I had not pick up any batteries during this trip, especially not the "N" batteries. I had, however, purchased a pack a few days before. I know it because I had to go to several stores before I could find "N" batteries. Apparently, when I got home, I didn't unload them from my reusable bag. When I placed the reusable bags into my cart, the batteries landed in the cart. The checker rang them up like a new purchase, as he should. I was so baffled, that he offered to take them back, and took them off of my bill. I explained that no, I really do need the "N" batteries, but that I thought they had been in my reusable bag. The checker and the bagger both looked at me like I was trying to steal this little $2.99 pack of batteries. I couldn't prove that I hadn't picked them up on this trip, so I ended up buying them, again. Not the end of the world, but really annoying!!!