How about trying to turn off the hack and then scanning again everybody that you have scanned with the activated pivot hack?
I know, GamingDude said that for him the achievement unlocked when using the hack, but as I said before the official game guide says otherwise ... So who knows ...
Maybe it's worth a try before you decide to start over again ...
100% Retail Games incl. all DLC:
GTA 5 * Far Cry 3 * Assassin's Creed 3, 2, 1 * L.A: Noire * Red Dead Redemption * Dead Rising 2, Case West, Case 0 * Mafia II * Alan Wake * Bioshock * Bully * Beautiful Katamari