One of the reasons my bookshelves are only loosely organized is that I like to "shop in my closet" - when I'm looking for one or another book, I often find something I'd forgotten I own & that is exactly the book I need. The opposite is more frustrating, when I can't find a book I not only know I have but am pretty sure where it is.
For 30 years, my friend Greggo asked if I had his copy of William Carlos Williams' A Voyage to Pagany. Nope, I said every time. Guess what I can't find anywhere? Yep, that very same book. Dang! I even dived into the stack at the back of my closet. I found second copies of quite a few books. I found a couple of other Williams books that had wandered to random shelves. But no Pagany. Dang. I bought a $5 e-book but I also wanted to read the intro - & I'm so used to the New Directions typeface that Williams doesn't sound like himself in the generic e-font.
It'll turn up! Or someone will stop by & grab it off a shelf without even looking for it.