Why is my character flying off screen?

Hi, everyone,

I have been working on a 2D platformer, and everything has been going fine for weeks, including my character's movement. However, after working in Unity for a few hours today my character started flying off screen (in the negative X and Y directions) upon pressing play. I did not change any code, and I think the only 2 things I did before everything was working fine and this bug appearing were:

1. Creating a new prefab for a spike that would do damage to my character.

2. Accidentally deleting my character from the hierarchy.

I thought these could be the issues causing my character to fly off screen, but I simply undid these actions (ctrl+z) until I had reversed both actions back to the state in which everything in my game was working fine. Does anybody know why this would occur? I have checked my character for any rogue colliders or objects, but none exist. I should also mention that this bug occurs no matter where I place my character (in the air, inside my ground blocks, etc.) before clicking play. Here is the movement script:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class player_1_controller : MonoBehaviour {
 
     //movement variables
     public float maxSpeed;
 
     //jumping variables
     bool grounded = false;
     float groundCheckRadius = 0.2f;
     public LayerMask groundLayer;
     public Transform groundCheck;
     public float jumpHeight;
 
     Rigidbody2D myRB; 
     Animator myAnim;
     bool facingRight;
 
     //for shooting arrow
     bool firing = true;
     public Transform arrowTip;
     public GameObject arrow;
     public float fireRate = 0.5f;
     public float nextFire = 0f;
 
     //for being alert or in combat NEED DAMAGE TUTORIAL
 
     // Use this for initialization
     void Start () {
         myRB = GetComponent<Rigidbody2D> ();
         myAnim = GetComponent<Animator> ();
 
         facingRight = true;
     }
     
     // Update is called once per frame
     void Update () {
         
         if (grounded && Input.GetButtonDown ("Jump")) {
             grounded = false;
             myAnim.SetBool ("isGrounded", grounded);
             myRB.AddForce (new Vector2 (0, jumpHeight));
         }
 
         //player shooting
         if (grounded && Input.GetButtonDown ("Fire1")) {
             firing = true;
             fireArrow ();
             myAnim.SetBool ("arrowShoot", firing);
             }
 
         //player in combat or alert NEED TO GET TO DAMAGE TUTORIAL TO DO THIS
 
     }
 
         void FixedUpdate() {
         
         //check if we are grounded - if no, then we are falling
         grounded = Physics2D.OverlapCircle(groundCheck.position, groundCheckRadius, groundLayer);
         myAnim.SetBool ("isGrounded", grounded);
 
         myAnim.SetFloat ("verticalSpeed", myRB.velocity.y);
 
         float move = Input.GetAxis ("Horizontal");
         myAnim.SetFloat ("speed", Mathf.Abs (move));
 
         myRB.velocity = new Vector2 (move * maxSpeed, myRB.velocity.y);
 
         if (move > 0 && !facingRight) {
             flip ();
         } else if (move < 0 && facingRight) {
             flip ();
         }
 
     }
             
         void flip () {
         facingRight = !facingRight;
         Vector3 theScale = transform.localScale;
         theScale.x *= -1;
         transform.localScale = theScale;
 
     }
 
     void fireArrow() {
         if(Time.time > nextFire){
             nextFire = Time.time + fireRate;
             if (facingRight) {
                 Instantiate (arrow, arrowTip.position, Quaternion.Euler (new Vector3 (0, 0, 0)));
             } else if (!facingRight) {
                 Instantiate (arrow, arrowTip.position, Quaternion.Euler (new Vector3 (0, 0, 180)));
             }
 
     }
  }
 }