DocuSign API Replace template document but keep fi

I want to use the existing fields from a server template over another document.

At first I tried attaching the document at the same level as inline/server. If I have the signer defined it gives me a 400 error, if I leave it off (did by accident) it completely wipes out the fields and shows the attached document.

Second I tried attaching the document to the inline template but that results in the attached document not appearing, it just operates like normal.

update

After adding additional debugging and research I now know that attaching it to the inline template was incorrect. After adding debug to read the 400 response I am getting this error:

"The DocumentId specified in the tab element does not refer to a document in this envelope. Tab refers to DocumentId 32475214 which is not present."

DocumentId is being set to 1 which is apparently wrong.

Which led me to this question on SO. In which a comment mentions that the ID kicked back from the 400 should be used. After I hard coded this ID I see the replacement operation is a success!

However I now need to find a way find and to plug that value in programatically.

Detail

I am using the DocuSign php sdk to help me build the data structure and access the api.

Use the listTemplateDocuments API to retrieve the documentId for the template.

The documentId retrieved in the above step should be used in the CompositeTemplate of CreateEnvelope request

{
  "emailSubject": "Tabs should remain from the Server Template",
  "status": "sent",
  "compositeTemplates": [
    {
      "document": {
            "documentId": "<document Id>", //Use the documentId retrieved using the listTemplateDocuments api
            "name": "Replaced Document",
            "fileExtension": "txt",
            "documentBase64": "RG9jIFRXTyBUV08gVFdP"
        },
        "serverTemplates": [
            {
                "sequence": "1",
                "templateId": "<Server Template Id Here>"
            }
        ]
    }
  ]
}