In Mamet’s The Spanish Prisoner (1997), Joe, for a genius, is a bit stupid. Maybe he hasn’t watched enough movies.
Jimmy tells Joe to “bring the Process” to their meeting in the park. Joe never mentioned that word to Jimmy. Though Joe is already suspicious of Jimmy, he does not notice. (Well, maybe he’s too angry to notice.)
The fake FBI agents tell Joe that Jimmy is working a classic Spanish Prisoner scam, though Jimmy has done almost nothing to set up such a story. If he says the “princess” is in trouble, will Joe hand over the Process to help her? Hardly. So why doesn’t Joe remark that it doesn’t fit?
When the police ask for something with Jimmy’s fingerprints, the plot requires Joe to take a day or so to remember the switched book.
Susan is the obvious suspect for the theft of Joe’s knife; this does not occur to Joe.