My wife, a native Argentine, took a taxi the other night. When the time came to pay, she realized she only had a 100 peso note. The driver took the note, fumbled around a bit and said "no llego," meaning he couldn't break the bill. He handed her back the note and she and her friend managed to round up the fee among them. When she took the note out later she realized he had changed the bill for a fake one. He was probably given the note in payment and felt it was OK to pass it along.