Hazou's main Social skill is Deceit (Inflict Consequences related to false information or pretending to let something slip). HOWEVER, convincing an enemy to hand over their paper requires Presence (Convince someone to do something by force of personality). Hazou's Presence is 15, and Presence rolls are defended against with Resolve (the Social Stress track). Most Genin with a brain will have Resolve 20; Hazou will lose these rolls more often than not.
We're not trying to convince them via force of personality, though - we're trying to give them false information (this person is a Proctor) and then let our stolen authority convince them to hand things over (as opposed to, say, convincing them it's in their best interests or something). Heck, "Believes you're a Proctor" could well be an applied Aspect or Consequence, and given the rules we're operating under I wouldn't say an actual Proctor is likely to need to engage in social combat to get a look at their word.
[X] Plan of Attack