There's very little evidence this is an actual lawsuit. The timing is highly suspect (at the close of day just before a long weekend in Japan), the suit doesn't appear in the database in the jurisdiction where it was filed, there's no court seal on the document itself and there's no indication on the CoinLab site (which would obviously be there if the matter has already gone public).
Anyone can draw up an official-looking statement of claim and "leak" it.
In a lot of jurisdictions you can file a Claim and have several months before you have to serve it. This is usually done to try to leverage your position without having to go through with the trouble of actually starting a suit since the clocks on response, examinations etc don't start to tick until after service. That would also be why you don't see an announcement on Coinlab's site. It's entirely possible that they'd rather get what they want out of Gox than burn years and millions of dollars in court.
As for it not showing up on searches, it was supposedly filed today. I highly doubt any North American court system is so efficient that online searches are updated within hours of pleadings being filed. This is especially true if the suit was filed near the end of the day.
Anyone should be able to order a copy of the pleadings when the court house opens tomorrow if they exist. I suppose it will be clear then.
