title: 404 "Change not found" message of push notification API and get changes API
body: <p>I have a question about push notification API.</p>
  
  <p>I've created web_hook URL under my service for push notification, so I can fetch URL for document change status with selfLink. </p>
  
  <p>But I get 404 codes sometimes when I fetch URL with selfLink.</p>
  
  <p>Please let me know why Drive API response 404 code sometimes.</p>
  
  <p>
  Scenario:</p>
  
  <p>Request body from google push notification server.</p>
  
  <pre><code>{
    "kind": "drive#changes",
    "id": "12345",
    "selfLink": "https://www.googleapis.com/drive/v2/changes/12345"
  }
  </code></pre>
  
  <p>Fetch URL under my server.</p>
  
  <pre><code>GET https://www.googleapis.com/drive/v2/changes/12345 
  </code></pre>
  
  <p>Response body</p>
  
  <pre><code>{
   "error": {
    "errors": [
     {
      "domain": "global",
      "reason": "notFound",
      "message": "Change not found: 12345"
     }
    ],
    "code": 404,
    "message": "Change not found: 12345"
   }
  } 
  </code></pre>