Very sorry to hear about your divorce and wishing you and your family a full recovery.
I am not an attorney and am not qualified to give you legal advice. Joseph made some good points. However, it may not be applicable if the divorce has already been finalized.
You did not provide many details… so will attempt to answer your question in general terms. An IRA / 401(k) belongs to the individual. It is not a joint account as what we are accustomed to seeing. So in short, a person can do whatever they want to do with their own property. A spouse must give consent regarding the beneficiary of a 401(k). This does not always apply on a distribution while living and certainly not after you are already divorced.
However, if his 401(k) is community property and/or you have a divorce decree that includes a Qualified Domestic Relations Order (QDRO), then he has potentially taken what may legally belong to you. Even without a QDRO, it is possible that a portion belongs to you, which will depend upon the community property and spousal support laws in your state.
The best thing you can do now is to consult with a lawyer that specializes in pension laws and/or divorce.
Jacqueline, we need a little more information on your question. We may need to know exactly what you mean by "went through" such as did he cash it out, is he taking disbursements, is he saying you can't touch it?
I can only give you generalities at this point as we would need to understand more of your particular situation in order to evaluate the circumstances. Also, I am going to give you what I know from a Financial Advisor standpoint as I am not a lawyer and cannot give legal advice. These are going to be general options for you of course so please make sure that you understand each one completely before making a decision. Each option should be driven down a little more in depth so you can get a clear picture of what it is you would like to do.
Generally speaking you and your divorce attorney can come to an agreement with him and his lawyers through a few different options. Each one of the points below should be understood in its entirety before you proceed with any one of the options.
Here are 4 common options for 401k plans during a divorce: 1) He keeps all the 401k and you agree to some other options or payments of comparable value. 2) You both split the 401k assets either equally or in another agreeable manor. 3) He liquidates a portion of the 401k to give you a lump sum. 4) He can roll a portion over to a 401k you currently have.
With each of the above mentioned options you both should speak to a tax specialist as each one has different tax consequences for both of you. Hopefully that helped you a little bit, and can help point you in the right direction. During a divorce you many need to seek help from a few professionals in this field as there are may topics to cover here. I can't give you complete legal (I'm not a lawyer but a financial advisor), financial, or tax advice, through the question mentioned because we would need some more information from your particular situation. These are general options that we have seen available through divorce so my answer shouldn't be construed as legal, tax or financial advice.
Just like they mentioned your question belongs to a lawyer. Every state has different rules in a situation like this, you may or may not have any rights. A divorce lawyer in your state can help you. As a financial advisor, we would be guessing without all the facts. I find it common to see spouses thinking they are divorced but each state has specific rules when the divorce is finalized. It is not necessarily the day the judge said you were divorced. It is the date according state law when the divorce is final. Now if that date was really 2 weeks ago, you should not have access to your spouse's 401k anyway. He has privacy rights. You may have QDRO rights and he may try to cash the 401k to avoid giving you his retirement, if that is the case you have to hire a good divorce lawyer. Sorry, we could not help you much on this board.