Heh, ouch! That had to be a painfull lesson!.
Rule number one - ALWAYS
look inside a locked safe before selling it!
I recall a similar story, Cant remember the full details, but he found, inherited, or something, an old safe which he feels pretty cheated by.
Anyway, basically this guy has a safe, a big tall heavy really ancient metal monster. He decides that it MUST contain valuables, that is the reason why he now owns it, so he proceeds to try to force the safe open. He tries picking the lock, then tries smashing it open, then a gas-axe, and finally melts his way inside. And he found......NOTHING.
So he decides to get SOMETHING for his trouble and sells the scrap, the scrap dealer then points out that it's a shame that the safe is smashed as it is worth thousands due to being highly collectable.
I don't know it that's an urban leg-end or not, but I can't remember the proper story anyhow. Amusing either way.