So yesterday I asked my istant Manager if I could see last week's time sheets because I wanted to see?

What your manager did is highly illegal. The company you work for can be fined into the millions for this. Skip talking to the manager, and the district manager, as it will be swept under the rug again. Call the Dept. of Labor, and report this. They will ask you for proof of this situation. Fax the info to them, and you will be reimbursed for any hours you feel you are missing. The company cannot retaliate against you for this. If they do, you will have a very serious lawsuit on your hands. Also, just to let you know. If your manager is receiving a bonus from the company based on the numbers she turns in, she has committed embezzlement. I have seen many managers go to jail for this!