Good one!

To OP, definitely don't let it get the best of you. Worse will happen on eBay. I have found myself in your shoes and wanting "justice". I agree with your hunch that this was shady and not purely a mistake. However, there is nothing to be done about it. If you can leave negative feedback, consider it. Then again, you don't truly know the whole story. Best not to start anything, which might result in a negative way on your end. For that reason, in my opinion, I would advise just moving on. Sucks, I know. But there are so many more bikes out there, don't sweat it!