well that's a clue! It seems to indicate that the document was created by some type of Book Title Page Template ... and perhaps the template is still attached to the document.

A title page template might have an area near the top for the title, an area near the center for the author's name, and an area at the problem for the publisher's name and year of publication. It would be jimmied so you could not type in the white-space area between those predetermined locations. It could also have key-bindings to hijack the Enter key and macros as well.

I was hoping if you clicked on Select Objects it might make an invisible image or table show up but it was worth a try.

I guess the next step would be to look on the Developer Tab, Templates Group, and click on Document Template to open the Templates and Add-ins dialog box. The text box at the top would show the path and name of the template currently in use for your document.