I had my airbag replaced by the dealer and later I was rear ended at a traffic light and my car totaled. The seat belt saved me. No airbag went off.
I wonder if they even replaced it??
Usually no airbag sensors in the rear of the vehicle...(rear-end collisions push you back into the seat w/a rebound handled by the seatbelt):
https://autoily.com/do-airbags-deploy-in-a-rear-end-collision/
https://autoily.com/when-do-airbags-deploy/