How to Add Scripts to GameObjects, that are within a Vuforia GameObject

I don't understand how I can add scripts to GameObjects that are within a Vuforia GameObject (ImageTarget in this case). When I run the scene, the GameObjects show on top of the imageTarget as expected, but the scripts I attached to them don't run. I have a simple chest on a map, with the following script attached to it:

using System.Collections; using System.Collections.Generic; using UnityEngine; using Vuforia;

public class Chest : MonoBehaviour {   void Start()   {     Debug.Log("hi");   }

  private void OnMouseDown()   {     Debug.Log("hi");

  } }

Neither the Start, not the OnMouseDown function will print anything in the console. What am I doing wrong?