It shouldn't matter how they found it, but as soon as the defect is found, it must be reported.
CAR51 clearly states:
Where a person who, in the course of his or her employment with an employer, is engaged in the maintenance of an Australian aircraft becomes aware of the existence of a defect in the aircraft, the person shall report the defect to his or her employer.
As far as I'm concerned, I'll report anything I see fit, not just what I'm "meant" to be looking at