If there is a visitation order in place, the mother moving without telling your husband where probably violates it in two ways, as most orders require the parents to keep the other informed as to residence, and she is denying him visitation. This likely take going to court, but it may be the only way.
If the mother has not informed CSO where she is, you may ask that they do not send her any support payments until she advises where she is living and her residency is confirmed.
As you have sent a letter to CSO, you may want to consider sending one to the judge who oversees the case, or copying him on the one sent to CSO. As with chicken soup, it couldn't hurt.
Finally, you may hire a private investgator to try to locate her. If you do, make sure that your give him/her a budget so that the expense does not get out of hand.
I hope this answers your questions. Please click Accept so that I may be credited for my assistance. Thank you and good luck.
DISCLAIMER: Answers from Experts on JustAnswer are not substitutes for the advice of an attorney. JustAnswer is a public forum and questions and responses are not private or confidential or protected by the attorney-client privilege. The Expert above is not your attorney, and the response above is not legal advice. You should not read this response to propose specific action or address specific circumstances, but only to give you a sense of general principles of law that might affect the situation you describe. Application of these general principles to particular circumstances must be done by a lawyer who has spoken with you in confidence, learned all relevant information, and explored various options. Before acting on these general principles, you should hire a lawyer licensed to practice law in the jurisdiction to which your question pertains.
The responses above are from individual Experts, not JustAnswer. The site and services are provided “as is”. To view the verified credential of an Expert, click on the “Verified” symbol in the Expert’s profile. This site is not for emergency questions which should be directed immediately by telephone or in-person to qualified professionals. Please carefully read the Terms of Service (last updated February 8, 2012).