You mentioned being hit by a trojan. I'd recommend starting there and letting them know about that. Then mention how your business's domain-name was stolen because of the security hole. Once they realize a business is being effected; hopefully that will get you a little more than ok thanks, here's your number. We'll call you.

I'm not saying this is an easy fix; but it IS Cyber-crime. I'd also consider talking with a lawyer if you can pony up the money.

And (not at you) ROFL down-voted for suggesting contacting the FBI. That's ok, keep paying taxes and not getting your money's worth. Government is there to help; they make a mess of things but they are better then a-LOT of the alternatives in other countries.