Changes to variables in script not being modified on objects attached to

I have a prefab projectile with a script on it that determines its movement. I had been modifying the values of the variable in a the provided text editor with the changes being applied to the prefab. This has stopped happening. Now I need to go to the prefab in the inspector and edit it there, reset the script from there. Why did this start happening and how can I fix it?

 using UnityEngine;
 using System.Collections;
 
 public class tidy : MonoBehaviour {
     public float CurveSpeed = 10;
     //public float MoveSpeed = 1;
  
     float fTime = 0;
     Vector3 vLastPos = Vector3.zero;
     // Use this for initialization
     void Start () {
     Destroy(gameObject,20);
     }
     
     public float speed= 5;
     public int count=0;
     // Update is called once per frame
     void Update () {
         vLastPos = transform.position;
  
        fTime += Time.deltaTime * CurveSpeed;
  
        Vector3 vSin = new Vector3(0, -Mathf.Sin(fTime), 0);
        Vector3 vLin = transform.forward*speed;
  
        transform.position += (vSin + vLin) * Time.deltaTime;
  
        Debug.DrawLine(vLastPos, transform.position, Color.green, 100);
         }
         
         
     }