You can respond by saying you have no information regarding what documents exist that support the facts. You do not have to provide the documents unless (1) they ask for the documents in a Request for Production of Documents and (2) they are in your possession which it sounds like they are not.
I agree with Ms. James, as long as you provided the information to the question asked truthfully and completely to the best of your ability you are fine. I would also object that the information sought is so old it is irrelevant and is burdensome, oppresive and meant to harass you and cast you in a false light.
As the request was an interrogatory, you are not required to produce documents, but you can expect them to send you a request for production of documents asking you to produce this information and if you don't have the documents any longer, then just tell them that as you can't be compelled to give them documents you no longer possess or that are not readily available to you, they can subpoena them from your lawyer, the court or DMV if they want and assuming they have not been destroyed by now?
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A special interrog can ask you to identify documents, so that they can next do a request for production or issue a subpena. If you know the date, name of the document etc you should provide it. Ask your lawyer if an objection can be made on work product privilege basis. The question asked you to identify the documents that support the facts relevant to your response. An argument can be made that requires your atty's work product as to which documents he believes support something. That may not be proper. He can ask what documents contain the facts, or discuss the facts. Just a thought.
The question asks you to "identify" documents, and not produce them. For example, you could "identify" the traffic ticket because you know it existed at one time, even though you cannot produce it now.
It's hard to imagine that this will have much relevance in a divorce proceeding.