I am not sure praying will work, but I won't go there. On the other hand, if you stop for a little bit, close your eyes, and mentally retrace your steps for when you last saw the object you lost, it may help. Don't force the issue, relax and focus on what you were doing... this helps me. Call it meditation if you like, I call it remembering.
Another tid-bit that I use: I decide on a way to organize stuff, and then I make a point of keeping that order. I used to misplace my wallet all the time because I used to take it out of my pockets (together with my keys) as soon as I got home. I decided that I would keep my wallet and my keys in my pockets. I only take them out when I need them or when I'm changing pants. I haven't misplaced my keys nor my wallet in years (probably jinxed myself right there /ubbthreads/images/graemlins/smile.gif)!
My son has a special bag where he keeps his Karate gear. He only takes gear out in his dojo, and makes a point of checking that he has everything in there and ready to go every time. Maybe you can do that with your books before travelling.