Look in the Front Office, next to the Library
You know how to work the file cabinets and other special containers in the mission from reading the README in DL or GL at mission start?So, Hint 2: Look in the Files for Library Book Checkout Cards"In this mission there is a money box which you can pick up, put down, and then unlock and open. File cabinets, dressers, and wardrobes have drawers you can open and look inside. Dresser drawers work like other containers, footlockers say. If anything is inside, when you frob to open them you get the contents, if any, in your inventory to inspect and decide whether to keep or discard. When you open wardrobe doors, wardrobes can have things hidden inside like a safe, or can give you their contents like a footlocker, or they can do both. File cabinets act like real world file cabinets. You have to open them to look at the files. The 1st frob opens the drawer selected. If there are contents that Garrett wants to read, the 2nd frob reads the files inside, otherwise it closes the drawer. If there were files inside, then the 3rd frob closes the drawer. File drawers can also act like containers, so a 1st frob may deliver an item into your inventory. Just because it does this does not mean there is nothing to read inside; that’s an independent issue. My suggestion is to always close file cabinet drawers after you open them."
If you still need a spoiler, PM me. I'm guessing you didn't realize that the files were more than props. That and if English is not your native language--right?--that all these readings are especially hard to wade through.