I agree with just try to focus and keep your mind on work. If you are the only one who has access to your drawer, perhaps you have been distracted and someone took a bill. Some people who do this can be very quick. When I worked in a Pizza place,I came up short and was sure that someone had entered my drawer. One suggestion might be to be prepared. Since you need your job and so much is at stake. I know it might be hard, but if you keep $20 or $30 on you then if you come up short again, you could put it in the till. I know it would be using your money to cover a mistake which you shouldn't have to do but it is better than being fired when it isn't your fault. Mistakes happen to good people. They don't care who's money it is, just that the drawer isn't short.