I Did Not Understand The Scene About Pinky's Ruse

Toward the beginning of the film, there is a scene where Pinky says something like "The police found our car and I mistakenly left my clip board with all the plans in that car". Gene Hackman says, "Why didn't you dispose of the car, like we had planned?" And Pinky says, "I took a detour to visit my niece". Now, right after this scene, the Black guy gets outraged and says "The whole plan is unsafe now. I am out of this plan". And he takes off in his car, with the nephew of Danny DeVito following him. I had no idea what this scene was all about. Can someone please explain? I thought that this was a ruse to make the nephew leave the whole operation. But, in a scene or two later, the nephew was still in the scheme. What was happening in this scene? What was that ruse supposed to achieve? Thank you!