please solve this riddle

[kamrez224]

you are all cleaver,scientifically ,electronically cleaver minds ,please can u solve this riddle for me. the riddle is " three friends went to the restaurant the bill came to £30.00 ,they contributed £10.00 each,when the waiter took the money to cashier. the cashier realized that he has overcharged them by £5.00,he gave the cashier £5.00 to give it back,the waiter was crafty he put £2.00 in his pocket and gave them back £3.00.
So the friends took £1.00 each back.
therefore they spent £9.00 each for their meal, now the riddle is £9.00 x3=£27,plus £2.00 waiter put in his pocket, that makes it £29.00 ,so where is £1.00 gone, i cant solve it please help