let fall between the cracks vs look at

let fall between the cracks

look at

verb
  • to face (to be presented or confronted with; to have in prospect) 

  • To consider. 

  • To observe or watch (something). 

  • To study (something) visually. 

How often have the words let fall between the cracks and look at occurred in a corpus of books? (source: Google Ngram Viewer )