If you have a contract that limits the employer's ability to terminate you, then you may have a valid claim. You should consult in person with an employment lawyer to get a careful evaluation.
My answers to questions posted on AVVO are intended to provide general information only, and are not intended to be legal advice. Employment law issues typically require a careful case-by-case analysis. Consequently, if you feel that you need legal advice, I would encourage you to consult in person with an employment attorney in your area.
It sounds like you have a written contract, in which case its terms govern the situation. You should sit with an attorney who can apply your facts to the contract and let you know your various options.
I agree that you may have an action for breach of your employment contract. You may also have a claim for self-publication defamation. That is, if you are required to tell prospective future employers that you were terminated for theft, that could also give you a claim.