While walking in a park, one morning, I found a Hundred Rupee note on one of the park benches. I picked it up, noted the number and took it home.
In the afternoon the plumber called on me to collect his bill. As I had no other moey at home, I settled his account with the Hundred Rupee note that I had found.
Later I came to know that the plumber paid the note to his milkman to settle his monthly account , who paid it to his tailor for the garments he had made.
The tailor in turn used the money to buy an old sewing machine, from a woman who lives in my neighbourhood. This woman incidentally, had borrowed Hundred Rupees from me sometime back to buy some household appliance. She, remembering that she owed me a Hundred Rupees, came and paid the debt.
I recognized the note as the one that I had found on the park bench, and on careful examination, I discovered that the note was counterfeit.
How much was lost in the whole transaction and by whom ?
I don't feel it's actually very relevant that the note is counterfeit.
If it circulates as currency, then it IS currency for the time it is
circulation. It could just as easily be a genuine note. Or a gold
ingot. On an IOU. Or - heck, why not - a stuffed alligator.
If it is mutually agreed that it's worth 100 rupees, then it's worth
100 rupees, simple as that. The tranactions don't become invalid just
because the note isn't an official one. (Thus the answer: Man finds a
counterfeit note a.k.a. stuffed crocodile on a park bench; it is
circulated as payment and come back to him but nobody wants to take it
off his hands anymore. He has lost exactly what he gained in the first
place. No-one has missed out, though they have foolishly given away a
stuffed alligator that would otherwise have made an interesting
conversation piece in their home.)