fired for false accusation

I worked for Stuart Anderson's Black Angus as a server/bartender for about a year and a half with no problems. In my last month of employment, a new general manager was hiired and started changing everything and causeing problems. My girlfriend also worked for the company as a bookkeeper/server. she was fired on a saturday for a legitamnet reason. On that following wednesday night, money was stolen from the safe. When I arrived at work on thursday i was called into the office along with the general manager, head chef, and district manager and questioned about my girlfriend's and my whereabouts the previous night. They basically told us that we did it and to return the money. After leaving the office, I started talking to the other employees and found out that they hadn't even known about the burglary and that i was the only one questioned. Being a black man, my first impression was that this was discrimination. I started feeling really uncomfortable so I went and talk to the night manager and asked him if it were ok if i took the next day(Friday) off. He told me "yes." When I arrived at work on saturday, I was told that I was being fired for job abandonment, because it was in the employee handbook that you must have your shift covered. Later, after looking throught the employee handbook, I contacted the manager and asked him where in the handbook that was stated. The first couple of times he hung up on me, then finally he responded with "that isn't why you were fired." A few months later I received a call from the police department asking me to come in for questioning. After giving a recorded statment over the phone, i went in and took a lie detector test. After the test the detective told me that I was cleared. when the case was closed, I obtained a copy of the police report and it stated that the opinion of people questioned led to the general manager. The detective went to the district manager and asked if they could question the general manager, but was told to drop the case. I need to know what i can do to either get my job back, or sue this company