When is Ground not Ground?

A while back I was working entertainment tech for a small convention, I was the Sound Designer and had inherited the Power Design (usually done by the Lighting department, but we did not find a Lighting Designer until very late). The event was held at a hotel with a 4-section ballroom, call the sections 1, 2, 3, and 4. The stage was set in section 4 and we had a social event in sections 1 and 2 on Friday night with the airwall between 2 and 3 in place. After the social event the airwall between 2 and 3 was...