Did this guy really forget the knife in his book or was it a dry run for the next 9/11?

No, not a dry run, but not just a mistake. The boy either wanted to be caught, or wanted to see if he could actually do it. My guess is he wanted to be caught so then he could scream. The ACLU and Al Sharpton, and the likes will be all over it. The though of arresting someone with a box cutter, hidden in a secret compartment in a book, I mean, I have box cutters hidden in books all over the place, doesn't everyone????