So anyway, to deviate ...
I was helping a friend of mine with chemistry work in the school library and I guess when she placed her textbooks on top of my pile of textbooks and then got up to leave, she took one of my textbooks with her and I didn't notice.
That night I had to bring home three other textbooks anyway so my bag was already heavy as it is and I certainly didn't feel the need to double check if I was missing one ...
She texted me this morning to say she had accidentally taken my textbook home. What made me really happy about this is that the simple text spared me so much panicking and anxiety because I would have thought I lost it somewhere. And of course I would have only realized that I was missing that book on Sunday night when I usually do all my procrastinated homework XD
So yeah, I'm just waiting for her to drop it off now!