The bitcoin system was always made to be a one and done type deal of a thing: almost always pure anonymity and no reversals. And on top of that you have Paypal who don't actually recognize or support, even to a point of condemning, bitcoin and bitcoin related transactions. Perhaps you could offer some amount to the forum or wherever else to help get your bitcoins back (assuming it's possible and may that be blackhat: your discretion).

Be that with Bitcoin or what, selling through Ebay is quite risky for anything that involves digital goods - including bitcoin, video games or whatever. Always got people making bogus stories that they've been hacked or in this case, they chargeback you.

In regards of involving the local police, good luck and hoping there's some cybercrime law or whatever in your locale that covers bitcoin.