it should be noted that at some point one of two things happened:
1) your account was compromised
2) onlinenic's system faulted
3) onlinenic's employee was not straight with you.
option (1) requires insurance; onlinenic MAY have it within their operating business insurance (if they are large enough company to have it), otherwise your insurance would cover it. if two insurance policies are taken out on the same item, it must be made clear who to contact, because if a cross-reference is made apparent to either underwriter, both policies would be invalid for that item (insurance is generally underwritten as a unified financial service)
option (2) and (3) require you to sue onlinenic for negligence, or fraud, respectively. in both option , a litigator will be happy to work on it for you.
trace down the exact days of your transfer of accounts away from onlinenic... was it before or after the new owner of the domain acquired it?
good luck
splonk