Big Sal's office is located upstairs of the main casino room of the Gomorrah. In order to reach this area, the Courier first must go to the bar room with prostitutes dancing on a stage. Next to the bar are 2 red mini couches; open the nearby door and walk up the sets of stairs. After reaching the pool tables, open the door on the far right side of the room. A Lockpick skill of 100 is needed.
The door to open the office is classified as owned, but picking its lock will not result in loss of Karma or fame. The Troike blackmail note is located inside the room's safe by the wall. There is no loss of Karma for opening the safe and taking the note. A Lockpick skill of 75 or higher or a Science skill of 50 or higher is required to open the safe.