I was once flying my aircraft, a Robin DR400/100, on a nice little day trip. Shortly after the initial climb out just levelled off and set up in the cruise, I noticed a 60mm long M6 Allen head bolt and penny washer rolling about in the passenger side foot well. As you can imagine this grabbed my attention. A quick check that all the controls worked normally then a gentle rate one turn for home. It took me and the licenced engineer a couple of days to find its origin. It turned out to be one of the bolts that secure the instrument panel to the airframe.
