You should immediately and privately consult with a lawyer who practices employment law.
You being fired for taking a cookie may be pretextual.
Do not write about your situation online or talk about it with anyone who is not your attorney.
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A lot more information is needed to decide if this was pretextual or not. I would suggest contacting an employment attorney who can provide you with a free consultation. Without knowing anything besides what you've typed, no attorney could decide if you have a case or not.