Back in the early 1970s, I had a 1971 Rick 4001 in fireglo with chequered binding (which I had bought new) as my main bass and a 1960s Hofner Violin Bass. As the Hofner was not being used, in 1974 I sold it (complete with original case, and possibly original strings) for the princely sum of £15. Even at that I thought I had ripped the guy off because it played like a dog and sounded like someone kicking a dustbin. I'd love to have it back now just to sell for a sensible amount.
I later sold the Rick to a friend to raise the deposit for my first house. He still has it, and I would take it back in an instant if he'd sell.
On the guitar front, I had an old Kramer aluminium necked jobbie that didn't appear in any catalogues I could find. My son took it with him to uni, and borrowed a case off a friend to carry it around. When he left uni, he handed back the case - with the guitar still inside!!! The friend has now disappeared, along with the guitar. A few months ago, one of my mates was talking about it and was sure he'd seen a pic of my old geetar. He tracked it down - a prototype for the thing that a certain Mr van Halen played for a short while, apparently. Bum.
Just to show that these things also work the other way round, I took another of my sons (I have a collection) to see Extreme last year and we had the "meet the band" package. My lad took along the N4 he'd bought off ebay for Nuno to sign. As soon as Nuno saw it he said "wow - my old guitar - there was only one made in that colour". One happy son!!