In Mr Robot, S01E05, the team attempt to social engineer Steel Mountain. When the supervisor they were expecting doesn't turn up, they alter their plan. Where does the team get the number of the supervisor?
If I am not mistaken they get it through her husband, the supervisor has only 1 contact listed (her husband) in all her online information. They went through her husband who apparently had more information online, including his medical records which most likely stated he was expecting results on a test or something.
They found her number most likely as first contact on the list of the medical record.