I figured out a workaround and thought that I'd share it with the community. It was a quick and dirty solution but it is a solution nonetheless:
1. The data connection for my submit to SharePoint Library automatically names my InfoPath form using the formula "concat(ID, Type, SubmitDate)" which uniquely identifies the form.
2. I added a text field in the form whose value get calculated after the form is initially submitted and an ID is assigned to the case.
3. Because the URL for the SharePoint Library is known and unique, and the name of the form that is added to the library is also known and unique, it is simply a matter of combining the library's URL plus the name of the form. I used another concat formula to add the URL of the Library and the form name to identify the URL for the form in the library: concat("SharePointLibraryURL", concat(ID, Type, SubmitDate), ".xml")
4. I then mapped a new field in my SharePoint List to receive this form URL so that I can access the form via hyperlink from the library and call it from an email generated by workflow.
I must note that this requires submitting the form twice; once to generate the ID (and form name) and once to update the SharePoint list item with the form's URL. It's an additional click, but it works.
--
David Alvarado