An Old Book with 50000 yen

A friend of mine went to a secondhand book shop.
He found a book with fifty thousand yen in it.
He couldn't take(steal?) the money.
So he decided to buy the book which had the money in it.
The shopkeeper didn’t notice it.
At last he succeeded in getting the money.
He divided the money with a friend who was with him then.
I should have been there.
If the man who brought the old book to the shop was having money trouble,
he was a fool.