cover story vs substitute

cover story

noun
  • A fictitious account that is intended to hide one's real motive. 

  • A story included in a publication that is highlighted on the front cover. 

substitute

noun
  • A replacement or stand-in for something that achieves a similar result or purpose. 

  • A player who is available to replace another if the need arises, and who may or may not actually do so. 

  • One who enlists for military service in the place of a conscript. 

verb
  • To remove (a player) from the field of play and bring on another in his place. 

  • To serve as a replacement (for someone or something). 

  • To use in place of something else, with the same function. 

  • To use X in place of Y. 

  • To use Y in place of X; to replace X with Y. 

How often have the words cover story and substitute occurred in a corpus of books? (source: Google Ngram Viewer )