If a Tamper status appears at any point, it will clear once the sensor is back together.
Follow the instructions to reassemble the sensor:
If the outer cover or any internal parts have fallen apart, they will need to be snapped back on first.
If the batteries fell out, make sure the positive and negative ends are oriented the correct way and reinsert them.
To get the main body back on the base, line up the protrusion on the base with the slot on the main body as shown below. Give it a clockwise twist to lock it back together.