raycast is returning object underneath another object

I’m trying to detect which game object the user has clicked, but the raycast is returning an object that is fully covered by another object. any clue how this is happening?

 //get where the user clicked the mouse in world coordinates.  Input.mousePosition returns a pixel coordinate
    			Vector2 worldPoint = Camera.main.ScreenToWorldPoint(Input.mousePosition);
    			RaycastHit2D hit = Physics2D.Raycast(worldPoint,Vector2.zero);
    			if (hit.collider != null) {
    				Debug.Log ("confirm collision with " + hit.transform.gameObject.name);
    				switch (hit.transform.gameObject.name) {
    					// cancel X button pressed
    				case "confirmCancel":
    					Debug.Log ("this.gameobject= " + this.gameObject.name);
    					// get the upgrade script to enable the collion checking again
    					shopBg = (GameObject) GameObject.Instantiate(Resources.Load("shopBg"));
    					upgrade = shopBg.GetComponent<upgradeScript> ();
    					upgrade.confirmShown = false;
    					// remove this screen
    					GameObject.Destroy (this.gameObject);

Seems obvious enough but also easy enough mistake to make… check the object covering it isn’t set to the Ignore Raycast layer and that it actually has a collider on it for the raycast to hit.