Hi Ross,

Yes, you can submit the Data to SharePoint Form Library without actually
publishing the form to SharePoint Form library

1.    If you have a button on the form click on the button to go to Button
Properties
2.    Select “Rules” and click on the “Add” button
3.    In the Rules window Click on the “Add” action
4.    Select “Submit Using a Data Connection” from the drop down
5.    Click on “Add” for Data connection
6.    Select To a SharePoint form library
7.    Give the location of SharePoint Form Library and the file name and click
on next
8.    Enter a name for this Data connection and click on Finish

Hope this will help you.