If a user deletes a Content item from a Document by mistake...How can I add that same Content item (with the same id) back into that Document?

If a user deleted a Content item (Test Case) from a Document (Test Suite) by mistake...How can I add that same Content item (with the same id) back into that Document?

I can export the Test Suite "as of" a previous date to see the removed content (Test Cases) and relationships. How can I add those Test Cases back into the document...then re-establish relationships? 

We recently updated from 10.5 to 11.0...but have not yet enabled document/content versioning.