You have to file the joinder pleadings in order for the retirement plan to be joined. Then the retirement plan has to be properly served with the paperwork, and that plan will generally have their own legal counsel that will file responsive paperwork and serve you a copy. Once you know who that legal counsel is, you might be able to contact them directly to request information and paperwork concerning the plan. Ultimately, a Qualified Domestic Relations Order (QDRO) will likely need to be done to determine the parties' interests in the plan, but that is normally not done until your divorce is completed. In your situation, I recommend that you seek legal counsel since this issue is somewhat complicated.
If your husband's pension plan was ordered joined by the Court, and if you had the pension plan served with the Summons, Pleading on Joinder, and Order of Joinder, you can propound formal discovery to the pension plan, i.e., Special Interrogatories and a Request for Production of Documents.
If you haven't yet received back a conformed copy of the Summons, the Pleading on Joinder - Employee Benefit Plan, and the Request for Joinder of Employee Benefit Plan and Order from the Court, you should go to the court clerk's office to see if the Court issued the Summons and signed the Order. If so, get photocopies of the conformed Joinder documents and have someone (other than you, over the age of 18) serve them on the administrator of the pension plan by mail. The pension plan ordinarily would file and serve a Notice of Appearance and Response of Employee Benefit Plan about 30 days after being served.
Once served, that plan becomes a party in the action, and you can propound discovery to the plan starting ten (10) days after service. Among other things to discover would be any loans to and/or withdrawals made by and/or on behalf of your husband from the plan, as well as the plan's periodic statements, Summary Plan Description, and model QDROs.
Your community property rights in your husband's pension plan should be preserved through a QDRO [Qualified Domestic Relations Order], signed by both parties, ordered by the Court, and served on the pension plan. You should retain, or at least consult, a Family Law Attorney regarding your rights in your husband's pension, as well as any other rights you may assert in your divorce case.
Please note that this answer does not constitute legal advice, and should not be relied on, as each situation is fact specific, and it is not possible to evaluate a legal problem without a comprehensive consultation and review of all the facts and court pleadings filed in the case. This answer does not create an attorney-client relationship.