That happened to me once about 7 years ago, I found a Nokia phone (no money though) in the grass in a lay-by on the Isle of Wight. It taught me one very important thing as I scrolled though the phone trying to make contact with the owner. Never leave loads of sexy messages, suggesting to the receiver what you would like to do to him! I found the owner, phoned her, waited and she drove to me to collect it. We had a bit of a chat, but she then left because she had to get back to teaching her class of children.
The only time I have found money was about three years ago in the middle of a local busy road near to our University, £30 in a wallet plus 3 photos. It looked like Mum, Dad and a young brother. When I took it to our local Southsea police station the desk Sargeant just said to me, "happens all the time mate, all the time!"