Their rental car remained untouched near the South Kaibab Trail.
Their phones went silent only minutes after they posted one final photograph together.
Search teams found no bodies.
No abandoned packs.
No blood.
No evidence explaining why two young women had vanished from a popular hiking route in broad daylight.
Three years passed.
Then, on July 11, 2015, amateur cavers exploring a remote section of the canyon entered a narrow cave high above a dry riverbed.