Hello,
I believe the solution to your issue is to create an Envelope, upload the documents with the escrow numbers that are specific to your clients and then apply the Template corresponding to the document in question.
This way, you will have the benefits of using a pre-prepared DocuSign Template to place the fields onto the unique document without having the "base" document itself, used to create the Template, sent out in the Envelope.
The following guide will outline this process:
https://support.docusign.com/en/guides/ndse-user-guide-apply-templates
If I have misunderstood, please let me know and provide further clarification, I'd be happy to help further if needed.
Kind Regards,
Damian