After tracking lost, camera locked at origin

Hello,

I am working on a ground-plane game in Unity 2017.4. When the player sets down their phone or looks too far away from the ground plane (likewise losing track of the content), the camera becomes locked at the origin and the content will then follow the player.

Is there any way that I can resume the ground plane tracking once the player looks back at a valid ground plane again?

Desired outcome:

Player loses tracking, then points phone back at a high quality ground plane surface. The content is then once again anchored to the surface so they may resume playing.

Thanks in advance.