Having something similar happen to me many moons ago is what inspired me to sit down and really figure out how to stop sucking at this. Of course, the guy who resold it way back then for that price is now crying his eyes out (while I'm about ready to jump off a @#$%ing bridge), as a name like that would be worth considerably more today.
Basically 100% of my drops get immediately re-registered so I'm sure it's happened since that time (I really don't care what happens to names after I'm done with them, so I don't keep track of who owns them, where they go, etc), but I'm at the point now where I'm very, very rarely dropping names anymore, save for ones that I've already mined for end-users and don't like for dev. The poor bastards re-registering them don't realize that they're getting very sloppy seconds, so I'm comfortable in the fact that I've did everything I could've done with a name before I sell or drop it and if someone makes money on it, it's based largely on luck.
But yeah, like Labrocca said- I'm kind of at the point now with buying names where I almost always come out ahead. It's where my screen name comes from. Getting a helluva lot tougher lately, tho. Used to be free money.