Poorly Motivated
Things happen because the script seems to require they happen.
The main character, Joe, never browses the Red Book while waiting for Jimmy (Steve Martin). Not once the whole time does he crack it open (even though in the opening scenes we see him furiously writing while on a work-vacation). Later he's got a ticket to Venezuela, and never once bothers to look at it. He has a cloth bag that is supposed to contain a camera; instead it has a handgun. He does not notice the difference. His lawyer friend (Ricky Jay) is murdered(?) and he immediately pats down the blood stain, leaves his glasses behind and and touches the murder weapon. In line at the airport a woman happens to lecture her kid over and over and OVER again about the book (people should have already made the book connection, but still, if you want to have this coincidence you don't need to beat our heads with it). He calls the FBI number on the card (she knew he'd take it).
Now some people will argue that it's plausible a person may never flip through a book containing the process or (especially plausible) bother to check a plane ticket. The problem is that no rational person could reliably pin their entire con a person behaving exactly as Joe does, which is why he's not a real character. Jimmy has decided he's going to kill Joe, but the protagonist needs to learn he's mic-ed and Fed. Marshals are on board. So what happens? He just wanders to the back, right where we see a Fed. who explains the whole thing to him. Everything happens because the script requires it to happen.