The Professor Was a Thief - Fantasy Short Stories Collection 3 - L. Ron Hubbard, L. Sprague de Camp - English

Primed for promotion to the World-Journal city editor, grizzled senior reporter Pop is stunned when it's announced that young Leonard Caulborn, the publisher's son-in-law, will get the post. Worse, the lad wants him out. In protest, Pop demands to be given a beat again and gets his wish. . . only now he's got just two days to find the "real" story about a dead-end assignment— a month-old physics lecture— or be fired.
When Pop starts searching for the story's source, a professor named Pertwee, he lands in the middle of the story of a century after the Empire State Building, Grant's Tomb and Grand Central Station all disappear. Apparently, Pertwee's the mastermind behind it all. But Pop soon discovers that, instead of inventing a new way to blow things up, the professor may be doing quite the opposite.

Caro1970

There seems to be two different books inside the file.