There is a flyer taped to the 2 hour only parking sign. It reads Found Monkey, but the k in monkey has been crossed out. And below the Sharpie drawing of a wad of bills is a brief sentence that reads: 

I found a sum of money at this location. Thank You
If this is directed at you, I'm sorry. Because if you lost the money it will be impossible for you to contact the person who found it. The finder has left no contact information.
Returning to the site where your money was lost, you'll quickly gather that the sum has been found. Because of this sign you learn that the finder was a keeper, that the finder has a sick sense of humor. And is artistic. Grateful even for the find. The finder wanted you to know that he found your money.
Or he doesn't care. It doesn't matter to the finder if you the loser return to the site or not. If you knew where you lost a wad of cash wouldn't you just return there? Shouldn't you try not to lose cash money in the first place? Unless of course alcohol was involved, which is a good assumption due to the proximity of the flyer to the bar across the street.
So maybe the flyer is a way to clear the conscious, or to artfully express a sense of gratitude.
I imagine the loser waking up in a flash. She remembers getting into the passenger side of a car (the street sign is on the right hand side of the road), and fumbling with a pocket stuffed with loose things. She races back to that scene the next morning when she realizes she didn't spend all of that money. But by then the wad is gone. And maybe the sign is up or maybe it isn't. Cash doesn't last on the street.
And then again maybe the loser didn't return at all, say, the flash never came.  
How much money and how it was spent is any person but the one who found its guess.
Suddenly, a young the young man walks past. He notices the sign and chuckles to himself. He looks down and around thinking he might find some money there, but there's no money there, neither a little nor a lot, just his beat up tennis shoes.