Missing Reference Exception

I’m trying to instantiate a prefab object that has a Audio Source in, because an error, I deleted the prefab and made it again, but now I have another error that says:
“MissingReferenceException: The variable Logro1 of Montañita1 doesn’t exist anymore. You probably need to reassign the Logro1 variable of the ‘Montañita1’ script in the inspector.”
When I step over the collider it works, I can listen the audio but the error is there, and it creates a clone that even if I put “destroy”, it still here.
The code is:

public class Montañita1 : MonoBehaviour
    public GameObject Logro1;
    public Text myText;

    void OnTriggerEnter2D (Collider2D other)
        StartCoroutine ("Logro");

    IEnumerator Logro ()
       myText.text = ("Encontraste tu primer fósil! Muy bien!");
       yield return new WaitForSeconds (4);

I don’t think you have assigned the variable of ‘Logro1’ in the inspector