No, I don't think it would be insider trading because the "insider" in this case, did not divulge confidential information to him intentionally. There was this one guy who got indicted for insider trading for overhearing a CEO at a racetrack, but he got off because the information got to him inadvertently. Insider trading laws are intended to protect the public from people within the company trying to benefit themselves or friends at the expense of the public - it doesn't stop people from investigating companies to uncover secrets that they can trade on. So if you hack into a company and trade on that information, you'd be guilty of hacking, not insider trading.
It's also questionable to say that the information traded on was "insider" knowledge, since it looks like the information he traded on didn't come from within the company. Anyway, this is just something I remember reading about once, so take it with a grain of salt.