He's been here a few months, has only a few trades. How is that great rep? Why would you risk that much if you know his profile and reputation is not worth $280? You've been here long enough, but still made a newb blunder.

Call Green Dot and report the card. Tell them you have the physical card and receipt you can take a picture of. They'll probably void the balance and ban his prepaid card or paypal that was used to load the MP. However, don't expect to get a refund from Greendot or CVS.