Joystick wont'go to it's default position when touch end

I created a script that will move the joystick along the touch position. The joystick will move just along Y axis, X axis is always 0.1 . When touch is ended the joystick should return to default position. I works, exept in the cases when a joystick is in limit of the Y axis, and when I move the finger a little bit on the X axis. Please, can someone explain to me why, and help me fix this.. Sorry for my bad english.

 #pragma strict
 
 //A class that will hold the boundary
 class Limit
 {
     var min = 0.3;
     var max = 0.7;
 }
 
 var relativePosition : float;
 //Variable that will hold the joystick default position
 private var joystickDefaultPos : Vector2;
 
 //Create an instance of the class:
 var limit = new Limit();
 
 function Start () 
 {
     joystickDefaultPos = transform.position;
 }
 
 function Update ()
 {
     //If the user touched the screen    
     if (Input.touchCount > 0)
     {
         //How many touches do we have?
         for (var i : int; i < Input.touches.Length; i++)
         {
             //Declare the touch variable tha will hold current touch:
             var touch : Touch = Input.touches[i]; //The touch
             
             //If we touch the guiTexture:
             if (guiTexture.HitTest(touch.position))
             {
                 //If the user moved the finger
                 if (touch.phase == TouchPhase.Moved)
                 {
                     var positionX = 0.1;
                     var positionYTranslation = Camera.main.ScreenToViewportPoint(Vector3(0.1, touch.position.y, 0));
                     var positionY = Mathf.Clamp(positionYTranslation.y, limit.min, limit.max);
                     transform.position = Vector2(positionX, positionY);
                     
                 }
                 
                 if (touch.phase == TouchPhase.Ended)
                 {
                     //Wen the user lifts the finger of the screen:
                     transform.position = joystickDefaultPos;
                 }
             }
         }
     }
 }