My bad mood

I work hard for the money and realized part of money gone from account. I not realized it until I see carefully my saving book account, it is sad because I cannot get back the money. I don't know who is the bad person, my dad told me must be someone working in the bank because the money withdraw procedure need to have identification card and also signature plus the saving book. But there is saving book for the person how he or she can take out my money?!