Notes
One of Our Asteroids Is Missing, a standalone novel by Robert Silverberg writing as Calvin M. Knox.

This volume is a "dos-à-dos" omnibus in the Ace Double series. It also includes The Twisted Men by A.E. van Vogt.

Publisher's Blurb – Page One
THE CASE OF THE HIGHJACKED ORBIT John Storm's return to Earth was triumphant: he was about to become a millionaire. Now there was only the routine job of validating his claim to the asteroid he'd found. But there was one problem – the computer had no record of Storm's claim. And stranger yet, the computer had no record of John Storm. He didn't officially exist!

There seemed only one possible explanation to the nightmare Storm found himself in – someone wanted Storm's asteroid. There had to be something on that tiny celestial body worth a great deal more than the reactive ores Storm had discovered. And that something was obviously worth the obliteration of anyone or anything getting in the way.