At this stage of the economist and gaming intersection, economists are still generally being pulled from the outside of the gaming industry. Finding exploits is not something that they've really had to think about in the way a gamer has.

I wouldn't blame him for it. Besides, all systems can (and will) be bent, broken, or subverted. Perfect identification of bugs is pretty much impossible. You can get a lot of obvious ones, and assume that the rest are above the ability/will threshold of the playerbase.