Just an employee - accused of theft

I work at a check cashing store. Our customers have signature cards placed on file as a form of registration. We get checks sent back to us for various reasons: NFS, stop payment, counterfeit... There are a number of ways to handle collection for these items. The owner chooses the easiest and most convenient method that fits the circumstances. Just resently I had a customer come in the store who had previously cashed a counterfeit check. He signed a check (a good check this time) and passed it through the window to me. I then called the police to pick him up for cashing the counterfeit check. They came and began an investigation. One of the officers asked me if the customer could have the check that he was going to cash on that day. I informed the officer that the check was the property of the business for payment of a debt (the check had the indorcement of the business stamped on the back). Later, he said, "Let me in. Give the check to me." I told him no. To make a long story short, I am being charged with two misdemeanors: theft and obstruction of an officer.

I didn't think the DA would persue this matter because I explained to him that I did not take the check, the customer presented the check to me under his own free will. Also, that the check was property of the business and as an employee I could not give the check to the officer, who wanted to give it back to the suspect. The DA was very surly and sent me to get booked. I did not have a lawyer present, but I didn't say that much other than that I did not take the check and that I am only an employee and am not allowed to give business property to the police. He wasn't impressed.

Any ideas other than to get a lawyer? (I am in the process of attaining councel) This is a weird situation and when I read the definition of theft I thought the DA would not press charges. I was wrong.