Answer:
The block didn't slide due to balancing of gravitational force with friction force
Step-by-step explanation:
When the block was given a flick the force provided an acceleration to it and it moved up the inclined plane. when the block reached top it was expected that it would slide back but it didn't this happened because of the frictional force acting on the bottom the block which was balancing the gravitational force component along the plane and this prevented sliding back of the block.
static friction was balancing mg*sin(theta)
fs = mg*sin(theta)