“I tell this story – I mean, even as the first lady – during that wonderfully publicized trip I took to Target, not highly disguised, the only person who came up to me in the store was a woman who asked me to help her take something off a shelf. Because she didn’t see me as the first lady, she saw me as someone who could help her. Those kinds of things happen in life. So it isn’t anything new.”
But she told Letterman this in 2012
MICHELLE OBAMA: I thought I was undercover. I have to tell you something about this trip though. No one knew that was me because a woman actually walked up to me, right? I was in the detergent aisle, and she said — I kid you not — she said, "Excuse me, I just have to ask you something," and I thought, "Oh, cover’s blown." She said, "Can you reach on that shelf and hand me the detergent?" I kid you not…And the only thing she said — I reached up, ’cause she was short, and I reached up, pulled it down — she said, "Well, you didn’t have to make it look so easy." That was my interaction. I felt so good. ... She had no idea who I was. I thought, as soon as she walked up — I was with my assistant, and I said, ‘This is it, it’s over. We’re going to have to leave.’ She just needed the detergent.