Riddle Me Silly!

[~Harmony~]

[thanks to www.riddles.com]

there was once a rich man.He walked out of his
roomand left a twenty dollar bill on the table.when he returned,it was
gone.first he asked th maid if she had seen the money.she said she
found itand put it under a book.when they looked,the money wasnt there.
he then asked the butler.he said he put it between pages 32 and 33. so
he opened the book and looked,but it wasnt there.however,after looking
in the book the rich man now knew who stole the money.who was the
theif?how did he know?