I'm afraid the knickers would have remained where they had fallen, with a word to neighbour that she was having a laundry malfunction.
I don't think OH or myself overly worry about offending people, just rely on good manners, tact and a bit of social awareness.
The area that bothers my OH the most is contact with children. We both get uncomfortable when small children are unsupervised, particularly at the seaside. Last summer, a naked boy, aged around 3, was just wondering about, and no one seemed to go near him. He eventually found his family a lot further away, and they were oblivious to his adventure.
We have had many discussions on this kind of incident, and OH will never intervene, unless they are drowning.
Sad indictment of the world if we are afraid to comfort a lost child and take them to safety.