When a document placeholder has not been received, there is a "Request Form" link available in the status column of your documents list.  

Click that link to view your document request form.  Click the "Save as PDF" button at the top of that page.  A PDF version of your request form will be downloaded to your computer.  You can attach that form to an email that you send to your writer from your own email program.  

Here is what the PDF of the request form looks like.  Notice the button on the top right.