Please an answer to this riddle?

3 people went into a cafe, they ate and the bill was 25 dollars, each one gave the waiter 10 dollars, he took it to the cashier, the cashier gave him 5 dollars to give the people back. He took 2 dollars and put it in his pocket then he gave each one 1 dollar back. So they technically paid 9 dollars each. 9+9+9= 27 dollars, plus the 2 dollars in his pocket 29 dollars, where's the lost dollar?