Parking Sensor problem

Hello,

It looks like someone has reversed or rolled into the rear of my car. While there and no dents or cracks, one of the seams between the bumper trim and the offside quarter panel has popped. The main issue is that the parking sensor now only starts to warn when I am about 2 metres from the object behind. It is also picking up the curb and objects to the side of the car.

My conclusion is that the sensor has probably been dislodged in the knock. Does anyone know where it is located?

Also is it possible to purchase a trim clip from Toyota to replace the one that has popped out/broken?

I did call my local Toyota service centre but they want £150 just to investigate!