Mine was undoubtedly this:
I was working in Bracknell at the time (and living in Swindon). It was a bit of a quite day at work, so I said to my work mate that I was going to clean the back of the car out, and tidy all of the work equipment up (I had a 4x4 at the time).
I'd had band practice the night before, so had my guitar in the back, in it's protective case….it was a Rickenbacker 360……(not showing off, but it adds a bit of depth to the story). I took the guitar out and put it on the verge where we were parked, and then tidied the rest of the equipment up. Once I;d finished it was around home time, so we headed off home on the M4. As I was just pulling off at the junction, a horrifying thought struck me and the blood drained from my face - I said to my workmate to quickly check in the back of the car and see if my guitar was there. It wasn't of course, so I quickly dropped off my workmate and started to drive back to Bracknell in the blind hope that it would still be on the verge. It was hammering it down by this point, and there was a crash in the lane next to me.
When I got back to the place where I'd left it, sure enough it was no longer there. I think I might have cried or something - but then I thought, there was no harm in trying the nearby houses and seeing if they had picked it up. I tried the first house and there was no-one in, then tried the second and a guy opened the door. I asked if he'd seen a guitar on the verge and he said that one of his neighbours had found it. I then went over to the house and his son answered the door - I explained that I had lost my guitar and understood that his Dad had found it and the kid said that his Dad had taken it to Bracknell police station.
so the next day I picked it up from Bracknell police station……I thanked the bloke profusely, of course.
Fucking lucky that!