I would not entertain getting the bike back and refunding/relisting... Let it happen and it becomes a habit. This person was probably trained by others before you to think they can just return what ever they buy.
Unless the buyer was duped, they need to learn some self accountability.
Tell them to HTFU and ride.

Having been on both sides as a buyer and seller, my one non-compromising rule, which I emphasize during the first discussion, is that actual voice contact is made immediately prior to meeting. (I mean, like turning the key within 60 seconds and heading out.)
Flaky buyers don't like it and this gives the seller a chance to let you know if someone is coming to look at/purchase the bike ahead of you.


Edit: dhorn33 posted while I was composing...
I'll reserve my opinion on that case until I know the circumstances of the ruling. In some states, if you sell 3 or more cars a year, they consider you a hobbyist/dealer. That changes the rules.