And why would someone take your domain, but leave the name servers still pointing to your site so you would not know. More importantly, how could the domain be transfer without you knowing if the email address in the domain contacts was correct? And you have other domains, but that is the only one taken...?
All the weird questions aside, I would approach this as if you transferred the domain and forgot about it. Contact the new registrar and tell them you don't have any of the account information for the domain. They will make you jump through some hoops, but you may get access to the account at the registrar. After all, it's pointing to your site and you do have the original transfer emails that show past ownership. If some other person owns the account, you may not be able to get into it, but you may learn who that person is and perhaps what other domains they have.
If you domain was stolen (possible, but unlikely IMO) then the crook many have many, many domains and not be bothering to change name servers and just be trying to sell them. Either your domain is no so great, or they have so many domains they may have forgotten about yours.
That is how I would approach the problem. If someone does have your domain, Hound the current registrar to get the current owner to produce proof of their ownership. It sounds like you have that and they won't. Good Luck!!!!
P.S. One more thing: See if you can get some information from Name about the transfer,like the IP address, email address, or anything else that may help. I don't think a lawyer can help you if you don't have evidence of what happened and who was involved. And if you have that the registrar should comply. And you could try contacting the CEO of Name.com. I have in the past and found him to be a really good guy. Just don't expect too much and blame them. There are safeguards in place to prevent this kind of problem even if they fail.
