I don't see how you're reaching this conclusion. He said, there are no publicly available contact methods that have "yielded any luck". He didn't say there are no publicly available contact methods or that he didn't e-mail yahoo's "security" e-mail address.

I'm reaching this conclusion because the only person he mentions emailing is Yahoo's CEO.

Pretty sure that if he's actually talking with Yahoo and the FBI then someone would have pointed him to that address if he really hadn't found it himself! More likely, they just told him "hang on, we'll look into this.. eventually" and he felt this was important enough that a delay like that is unacceptable. Which it is. If you know you've just lost all your customers data, you don't wait a few days to tell them - you schedule a press release for same day release.