The Treasure Hunt is a time-limited event consisting of several steps. Each step has its own treasure item item goal and reward. You can collect treasure items by collecting them in levels. 

When you reach the treasure item goal of a step, you get a reward and move on to the next step. When you complete all the steps, you win the Grand Prize. 

If you lose or quit a level, the special items collected during the level are not counted towards the Treasure Hunt event.