She didn't do intentionally
A girl went to the shopkeeper to buy shoes and gave a 500 rupee note to the shopkeeper. But the shoes cost only 200 rupees and the shopkeeper didn't have the change rupees to return to the girl.
He gave that 500 rupees note to the neighbour shopkeeper and got the change. He returned 300 rupees to the girl after charging 200 rupees for the cost of shoes.
The girl left and the neighbour shopkeeper noticed that the 500 rupees note was fake. He returned the fake note to the shopkeeper and got the true 500 rupees in turn.
What is the total loss the shopkeeper suffered in this event?
Clarifcation: The fake 500 rupees note is of no value i.e. 0 rupees.