It was probably drug money. If I found a wallet with ID and cash inside I would contact the owner. If I find cash in a brown paper bag I will look around and if nobody is looking....yipee!
I live out in the country and have heard there are drug dealers out here. Local inmates work on the garbage trucks and clean-up right-of-ways around here. One day they were working cleaning the right-of-ways and one inmate found a package in the road ditch in front of my house, it was $30,000. He could gotten away with keeping it except him and another inmate got into an arguement about it(greed). Man I wish it had been grass cutting day and I had found it.