I thought i would put my 2 cents in here. You asked about how to prove. For 1 week maybe 2, keep a list of items that he is selling together and jot them down. If you have his billing address (which i would think someone does), then call the pd. I work with law enforcement across the country, so if you need any help on that side, just send me an email.
Now about ebay, I used it this week for stuff and im done and about to withdrawl posting. After 100 nigerian scammers, they are questioning my products. I understand that i am a new seller but I would perfer the buyer to question me, then a corporate offices with a call center full of people.
I would file first and foremost with the AG of the State of California as well as the Ethics committee of the State. Their employees are only following procedures that were put in by corporate so that goes all the way to the founder in which we all know is running for office.
I have dealt with so many people across the world and have no issue with pulling the plug on a millionaire that got rich off of defrauding people and that is exactly what she is about.
Again if you need help, please feel free to contact me. I will be the bad guy. ;) Im just tired of seeing good people get jacked while honest wholesaler and distributors like me are questioned constantly.