Damn.. That's fucked up. You should find him somehow sooner or later anyway..
Don't know if it is possible now, but you could use service like afraid.org before and with just one change by his side, you'd be able to change your dns really quickly from your afraid.org panel..
I'm not an expert in this, but if you find him, do that..
Other tip I have is to contact the register to domain, by the rules of most domain registars out there, the person should give valid information on the way they could contact him, so he needs to be reachable. They wont share the contact but it might help if you explain them whats going on
