Last night, AA 4161 RDU > JFK was delayed nearly 2 hours because at pushback time it was discovered that the First Officer was missing required pages in his book. They first tried to get the pages photocopied from another book but were unsuccessful. They announced that the correct pages needed to be flown down from Pittsburgh and offloaded the pax for approximately an hour awaiting the arrival of the pages.

We reboarded exactly 2 hours after the original boarding time and had an uneventful flight to JFK.

I've not heard this reason before in hundreds of flights over 4 decades and am curious about "the rest of the story." Would appreciate any insights about what was really going on.