[1]https://www.quora.com/q/techinsider/The-NSA-phone-spying-program-exposed-by-E
dward-Snowden-didnt-stop-a-single-terrorist-attack-federal-judge-finds?ch=99&sha
re=6c3ad8ea&srid=9CvSA

   Jim Bell's comment:

   However, I wonder if that this phone recording was ever used to
   backtrack to get other evidence.

References

   1. https://www.quora.com/q/techinsider/The-NSA-phone-spying-program-exposed-by-Edward-Snowden-didnt-stop-a-single-terrorist-attack-federal-judge-finds?ch=99&share=6c3ad8ea&srid=9CvSA