I was out doing some street photography with my M2 and pulled up this rangefinder to capture a woman sitting on a bench in a small town reading a book. A small girl was walking by and I took the shot.
Walking back to the car I was internally proud of the shot until I opened the car door and was putting the camera in its bag when I noticed I had a 90mm mounted on the camera and I just knew I had used the entire 35mm frame lines to capture the image and I was very close to the action.
So I knew I did it, shot the wrong #$%^& frame lines on a unique unrepeatable moment. Have you done this too?