I was on an airplane on a flight back from Boston a few years ago, and as I was getting off I opened the overhead compartment to take out my coat. It was a black peacoat and therefore fairly indistinct in appearance. After taking it out, I realized that my mother, who had been sitting next to me, was holding my coat and that this one was not mine. I set the coat on the seat and got off the plane.
As we were waiting for our luggage, a woman came up to me and asked if the coat I had was hers. I told her no, it was mine, which was true. She said she had looked in the overhead compartment for her coat and could not find it, and she was asking around if anyone had taken it by mistake. It was at that moment that I remembered taking the wrong coat and setting it on the seat. But I only said "I'm sorry, I hope you find it."
It somehow seemed like too much effort to tell her about it.