Lost rare first edition paperback of 'To Kill a Mockingbird' at Zilker Park while walking a dog.

I lost a rare first edition paperback of 'To Kill a Mockingbird' while walking my dog at Zilker Park. I had placed it on a bench to take a photograph of my dog, and when I went back to grab it, it was gone. It means a lot to me as it was a gift from my grandfather, and I would love to have it back. If anyone finds it, please contact me. Thank you!