Green paperback mystery with notes

I found a paperback mystery novel this afternoon around 2:45pm outside the Jacksonville Public Library on N Laura St, Downtown Jacksonville, right near the main entrance. It's a green Penguin Books edition, about 336 pages, with a creased spine and a small coffee stain along the bottom edge. There's a blue bookmark sticking out between pages and a sticky note tucked inside the front cover that says 'For Sam' in neat handwriting. The jacket is a little worn, but the pages are clean, and the vibe is cozy-serious, like it traveled through a few coffee breaks. If you recognize the bookmark or the note, please get in touch. I would be glad to return it to you.