My character moves under the terrain at strange Y position

Hello, i’m actually making a Flappy Bird clone, and when i started to work on the menu and reloaded the main game scene, something strange happened.
When i pressed the play button, my character instantly moved under the terrain at 9xxx position( I don’ t remember the exact one).
I think this is something related to the physics engine, because if i remove the Rigidbody component attached to my player, the player doesn’t move, and the exact thing happen if i remove my Sphere Motion script.
This is my Sphere Motion script text

#pragma strict
var force:int;
static var animate:boolean=true;
static var canDie:boolean=true;
static var canMove:boolean=true;
static var points:int;
static var record:int;

function Start(){
force=force*1000;
gameObject.rigidbody.AddForce(Vector3(0,force,0));
}
function Update () {
record=PlayerPrefs.GetInt("record");
if (animate){
	animation.Play("dragon_idle");
		}
	if (Input.GetKeyDown("space")){
	//if((Input.touchCount>0) && (Input.GetTouch(0).phase==TouchPhase.Began))	{
	if (canMove){
	animation.Stop();
		animation.CrossFade("dragon_panic");
		gameObject.rigidbody.AddForce(Vector3(0,force,0));
		}
		}
		}
function OnCollisionEnter(col:Collision){
	if(col.gameObject.tag=="Obstacle"){
			Inventory.move=0;
			Inventory.canInst=false;
			SphereMotion.animate=false;
			if (canDie){
			gameObject.animation.Play("dragon_die");
				Debug.Log("Collision");
			canMove=false;
			canDie=false;
		
			}

}
}

Thanks to everyone for the answer, and may a get an explaination for what is happening, for avoiding me to do the same error?

thx :slight_smile: