There are three sides to every story, yours, mine and the truth.
My guess is just that, we are not hearing the whole story. Just from the cursory read of it he (the author) mentions that the seller contacted him with a “frantic email” asking for the manual back. The story also alludes to copyrighted material being involved.
I also find it hard to believe that the FBI is watching every questionable transaction on every auction website and is scouring every single BBS looking for anyone who might be an evildoer.
I seem to recall a once famous “hotline” the FBI put up immediately after 9/11, one which they sang of from the highest peaks and mountains each and everytime a media microphone was nearby.
And that very same hotline was the source of hundreds of tips which fell through the cracks, tips that later turned out to be legitimate including one where a lady saw a man on a flight somewhere out of the Midwest, thought see recognized him and later saw a picture of a man on the FBI’s wanted list, those so called “persons of interest” she then called the FBI and they told here to quite watching so much cable news!
She finally called a reporter for her hometown newspaper that did some digging and lo and behold guess who was on that plane?
Yep you guessed it!
Same thing happed with the recent DC sniper shootings, hotline again and the FBI was out to lunch.
There is simply not enough federal manpower in law enforcement circles to undertake such a massive venture, the FBI as well as every other single federal law agency is at the breaking point.
I find it had to believe that the FBI moved on this guy simply because he sold a flight manual to someone on ebay, there is more to this story I assure you.