There is a chance you might be approved for unemployment benefits since you were terminated. If you haven't already done so, apply for them at once.
You were terminated for "gross misconduct." In other words, the company maintains that this behavior was so egregarious, so bad, so wrong that you should have known it was wrong to do it even one time, even without being warned, being given second chances, etc.
However, with the behavior being so widespread, with so many people having done it, and there being no wholesale termination of all the employees who were known to have been participant, you could reasonably argue that you did not know that your accepting discounts was misconduct, that you did not realize that it could result in your termination. You'd want to mention that you had been working there eleven and a half years without a warning or a disciplinary action, that you did not intend to lose your job, and that you had knowledge of several other people who were working with you who got the innappropriate discounts and were not treated the same.
But unemployment insurance, if you happened to be qualify for it after the appeal process, is all the satisfaction you can get. There is no law against terminating an employee for just about anything they want to terminate you for, or no law that says they have to treat everyone the same or be fair in their actions.
Hint to you. When discussing this claim after it is filed, or when filing, do not refer to what you did as "stealing food." Call it accepting unauthorized discounts on food. Because saying you were fired for stealing food automatically clarifies that you KNEW you were stealing, stealing is wrong, you admit it, and you know you could be fired for stealing, whether everyone was or not. This certainly weakens your claim. That everyone was doing it doesn't justify something you flat out identify as "stealing." You get no points for your outstanding frankness, would need to present this as you didn't see it as stealing, just something those women in dietary were doing as a favor for their friends. I'm not telling you to lie, but I'm saying that bravely owning up to the worst spin you can put on this action is not a good idea.