@Zik:
Yes the strawhats also searched foe the bomb but they all first took down the top ranks of Baroque Works before that. With how they split up to end up in that situation and Vivi not even bei g stopped by anything I dont even remember what she was doing while SH fights were going on that she failed to reach Kohza.
Vivi did reach Kohza - they met up at the royal palace when Crocodile and Ms. All Sunday were smacking down Chaka and the other royal guards and trying to get Cobra to talk about the Pluton. A bit later there was even a pretty big panel of Kohza and the royal guard meeting the oncoming rebel army at the foot of the palace stairs holding massive white flags intending to call off the fighting then and there, only for a Baroque Works agent in the royal guard to shoot Kohza in the back before he could explain what was going on.