Do you have e.g. a bind .jnl file of one of the NS behind the zone, because you can re-create the text form of the zone from the binary zone state in journal.
Do you know how to talk to the Registry, rather than a registrar, because you own the domain, and even under contract for service, its your name, not their name unless you signed a very awkward contract.
Do you have a lawyer? I think you need one.