detain vs slip through the cracks

detain

verb
  • To keep someone from proceeding by holding them back or making claims on their attention. 

  • To put under custody. 

  • To seize goods for official purposes. 

  • To keep back or from; to withhold. 

slip through the cracks

verb
  • To escape notice or lack sufficient attention. 

How often have the words detain and slip through the cracks occurred in a corpus of books? (source: Google Ngram Viewer )