Could not resolve reference - invalid error

This is my schema with no reference to inventorySystem but I keep getting the error: Could not resolve the reference #/components/schemas/inventorySystem at line no 60 though it has only 55 lines! Any help would be much appreciated.

openapi: 3.0.0
servers:
  # Added by API Auto Mocking Plugin
  - description: SwaggerHub API Auto Mocking
    url: https://virtserver.swaggerhub.com/KRISRAJZ/Customer/1.0.0
info:
  description: This is an API for HPlus Sport Customers
  version: "1.0.0"
  title: Customers API
  contact:
    email: you@yhplussport.com
  license:
    name: Apache 2.0
    url: 'http://www.apache.org/licenses/LICENSE-2.0.html'
tags:
  - name: customer
    description: customer related calls
paths:
  /customer:
    get:
      tags:
        - customer
      summary: searches customer
      operationId: searchCustomer
      description: |
        By passing in the appropriate options, you can search for
        available customer in the system
      responses:
        '200':
          description: search results matching criteria
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Customer'
        '400':
          description: bad input parameter
components:
  schemas:
    Customer:
      type: object
      required:
        - name
        - customerNumber
      properties:
        customerNumber:
          type: string
          example: 'Cus001'
        name:
          type: string
          example: 'Raj'
        phone:
          type: string
          example: '728-234-234'