Yeah, their web site is vague. However, from this article, one can glean that 1) it actually happened to *a lot* of domains and 2):

despite panix.com's belief that their registrar locks were set, somehow the domain was transferred...

From a discussion of what went on, we hear that:

...high-value domain names are being monitored continuously for changes in their lock status -- once they are unlocked, a wave of fraudulent transfer requests arrive from some of the minor registrars (e.g. ones in China or Korea), trying to steal the domain.

Sounds like there are still a few rogue registrars out there.

Panix may have unlocked or Dotster briefly screwed up... or... ?