They cannot find every last book they published from the year 1880 until now.
In a delicious irony, the WTS today is in the same position they put dubs in back in the 1970s. When they heard publishers were "selling homes and businesses in order to finish out the last days of this system in the full time ministry," they fell all over themselves applauding that behavior. In retrospect, that behavior was foolish and encouraging it was almost criminal. So why'd they do it?
The WTS didn't worry about it because they were betting the ranch on the end coming... if not in the fall of 1975, then very soon after. In other words, there was never going to be an accounting! Armageddon was going to wipe the slate clean and any erroneous speculation would be lost the excitement over their being right about the one really important thing.
Now 30 years have gone by and all those silly pronouncements, speculations, charts and graphs and chronological faux pas have come back to haunt them, thanks in large part to the unforeseen: the internet. They must be down on their knees nightly in Brooklyn, praying that the Big A comes tomorrow. They thought it didn't matter what they said or did because time was on their side. It wasn't.
Thanks in large part to the internet, the next decade is going to be a painful one for the WTBTS. They've been counting on a miracle, much like a football team that is down points in the waning minutes of the game and, having just fumbled, can only watch the minutes tick down while the other team runs out the clock.