Young CAM Jansen and the Zoo Note Mystery

Cam and Eric's class is going on a field trip to the zoo. But Eric can't find his permission slip, and without it, he can't go on the field trip. Where did it go? Did he drop it somewhere? Was it stolen? Will Cam Jansen's amazing memory help to find Eric's permission slip in time? Or will he have to sit in the principal's office all day while the other children go to the zoo? Hurry, Cam, time's running out!