Thanks
If you're talking about a civil matter, it could be an expensive exercise if they've been even half-way cautious. Hell, pirate's RL identity was known but it's unlikely he'd have been facing any consequences at all had the feds not got involved.
You could certainly try to get an order for theymos to disclose any information the forum has related to the account. That information may or may not be useful. Assuming that it looks promising, you could then try get an order for email providers and/or ISPs to disclose information they have related to the account - which may or may not be useful depending on how cautious the other party has been.
Generally speaking, it's not going to be worth the effort for small claims matters. Even if you're talking about being scammed out of large amounts, litigation is expensive and often protracted and prevailing in court is meaningless if the other party cannot pay.
You're better off taking measures to protect yourself against being scammed than hoping that a lawsuit will bring you a satisfying result in the event that you are scammed.