If you are rich or you have lots of bitcoin so that you can hire a private investigator or someone who can get information on people, there's a chance you can track them down.
It is really a sad thing but it is the reality. The thing is bitcoin is so far not declared as legal currency and because of that, you do not need to pay anything in the form of tax and that you cannot even take any kind of legal action against the ones who are doping any kind of illegal activities in this. There is no such kind of rule or anything like that which can help you out in this regard.