It is fairly common for restaurants to have a secret menu that customers in the know are aware of, but the items do not appear anywhere on their actual menu. In-N-Out Burger comes immediately to mind with their Animal style burgers and fries, Flying Dutchmen and many other "not-so-secret-menu" options. There is a website called #HackTheMenu that lists numerous fast food restaurants and their secret menu items. Recently I found out that even local Hank's Creekside has a secret menu item! Our bookstore has the equivalent of a secret menu of it's own.
Have you ever looked for a play or the drama section at the bookstore? You probably had no luck in finding either because the drama section is "hidden" in the area where only employees go. If you ask, then we take you in the back, and show you where to find the section. Recently we needed to expand the section of books on CD and the most logical place was the four shelves housing the gay and lesbian section on the same bookcase as the CD's. We had no available space on the floor so that section was relocated on the bookcase behind the front desk.
Quite often a customer will come in the store, browse around for a while and, on the way out, say, "Thank you, but I didn't find the book I was looking for." There is a distinct possibility that the book they were looking for might have been "hidden" away in our back stock. We try to keep two copies of every title we have on the floor for customers and keep extra copies in our back stock sections. More often than I like to admit, we will sell both copies of a title and not realize that we now have no copies available for customers even though we actually do have the book. Howard noticed that we had not a single copy of a Tolkien title on our shelves. In our back stock we had at least thirty Tolkien books! We have now remedied the situation but it does illustrate the need to ask an employee if you don't find what you are looking for.
You should also ask if you are looking for an author and don't find any of their books in the section where you thought they would be filed. Customers frequently look for Catherine Coulter in the mystery section because they are hooked on her FBI series. They wouldn't have any luck because she started out writing historical romances so was a good fit for our contemporary/historical section. We haven't moved her since her output is about half mystery and half historical fiction these days.
Please ask if there is a category of books that you can't find, they just may be in a "secret" hiding place. Unfortunately small sections tend to get moved around fairly frequently when we expand our larger sections. You will probably need to ask if you are looking for mythology, foodie, writing, reference, poetry, Native American, comics or bibles.
One other "secret" section is our blind date books. Not that they are hard to find since they are located right in front of our check-out desk. We keep the title a secret, but for only $1.00, you can take a chance on getting a great book!