I am a law school graduate. What I offer is mere information, not to be construed as forming an attorney client relationship.
Here are the issues:
1. It sounds like you knew you were overpaid and never said a word.
2. If you knew and you cashed the check, you are liable, wrong social security number or not. If you did not know when you cashed the check, you have no liability because you are missing the requisite intent to steal.
3. As to the warrant, if you think you will get off on such a technicality, you are wrong. Court can still make the warrant valid as to YOU.
4. Ultimate conclusion, hire a criminal defense attorney and see what can be done so this can be just quietly taken care of.