Found another reference on the options page.

Author: Mikk3lRo

public/options.html

@@ -162,6 +162,7 @@ <h3>Example:</h3>
     &lt;option value="1"&gt;Option 1&lt;/option&gt;
     &lt;option value="2" selected&gt;Option 2&lt;/option&gt;
     &lt;option value="3" disabled&gt;Option 3&lt;/option&gt;
+    &lt;option value="4" hidden&gt;Option 4&lt;/option&gt;
   &lt;/select&gt;</code>
 </pre>
 
@@ -181,8 +182,8 @@ <h3>Example:</h3>
           <td>The attribute <code class="language-html">multiple</code> on your select box dictates whether Chosen will render a multiple or single select.</td>
         </tr>
         <tr>
-          <td>selected, disabled</td>
-          <td>Chosen automatically highlights selected options and disables disabled options.</td>
+          <td>selected, disabled, hidden</td>
+          <td>Chosen automatically highlights selected options, hides hidden options and disables disabled options.</td>
         </tr>
       </table>