Many years back I had a book titled 'Aircrash Detective' Not as sensationalist as the title may have one believe, it was an in-depth look into the workings of AAIB and others. A small exercise in there was to describe your wristwatch - without looking at it first. It's probably your most familiar posession, but could you describe it's appearance, winders, hands, face, etc. from memory? Eyewitness reports can only back up technical evidence, and the fuel inside the fin is a very plausible explanation for what was seen.