This quest is triggered only after wiping the raider settlement and bringing the Mr. Bishop's account book to Lynette. The Chosen One then needs to bring Lynette also Bishop's holodisk (or have it already in inventory when bringing the Bishop's account book, but this results in 1000 less XP reward probably due to bug as 1000xp for bringing account book is not given).
Bishop's holodisk is in his bedroom safe in New Reno, located in the wall of the northern most room on the top floor of the Shark Club. The safe has to be disarmed with the Trapsskill, and then lock picked. Failing to disarm the trap will set it off, it will also be set off by lock picking it before disarming it, a guard will attack and turn the whole Shark Club hostile, which disrupts all quests that require talking with Mr. Bishop. Approach Joanne and hand over both pieces of evidence.