was the entire site really behind tor? if that is the case, i wish you guys the best of luck to find him, otherwise if it wasn't just get the federal bureau of investigation or some other entity that cover cyber crime. they can force the hosting company to reveal the identity of the person/s.  an incident this large is almost certain to get caught. and when he/she is caught, you might be lucky and get all your coins back assuming the logs were still in tact/obtainable, or at least be ordered to pay back the BC.