Do PADDS have a "slide to unlock" password protection feature?
They just might.
Odo was there, too, and its entirely possible he could make sure nothin' happened to it.
I also find that very likely.
I mean, obviously something
prevented the 1947 humans from reading the guidebook (Quark and co. returned to the same timeline they left, so there was no contamination), and Odo retrieving it is as good an explanation as any.