This is less an employment law question and more business law. I would suggest posting your question again under the business heading to get additional answers.
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If there is no operating agreement for an LLC you will have to look at what the default LLC rules are for the state in which the LLC is formed.
You should contact an attorney to advise you on how to proceed.
The allocation of membership interests in an LLC are not simply determined by capital contributions. A person can commit capital, property or services in support of their value added to the LLC. With no operating agreement to the contrary, profits and are to be allocated on the basis of the value stated in the records of the LLC.
You are going to have to establish the value you added to the LLC, and are going to need a lawyer to help you litigate this case if necessary. Your initial issue is proving that you are a member of the LLC.