It happened to me as well - I don't know if the item was ever shipped (and if it was, if it went to the wrong address or something), but by the time I realized it had been a really long time (yes, I tend to be absentminded and not realize how long it's been), the seller was no longer a registered user, and I really couldn't do anything about it.
It was a definite learning experience, to say the least.
