title: Gravityforms not found message - WP Plugin hook
body: <p>I'm trying to hook onto the WP Gravityforms plugin's not found message.
  I've found a hook(gform_form_not_found_message) for this but it doesn't seem to be firing. What am I doing wrong here?
  My code:</p>
  
  <pre><code>function notfoundmessage($message, $id){
      $message = 'test';
      return $message;
  }
  add_filter( 'gform_form_not_found_message', 'notfoundmessage', 10, 2);
  </code></pre>
  
  <p>I tried several thing like writing the function inline, including it from the main plugin file, including it in an oop way but none of them seem to work. I was thinking that maybe I need to require a gravityforms Class but I can't find anything about that in the documentation.</p>
  
  <p><a href="https://docs.gravityforms.com/gform_form_not_found_message/" rel="nofollow noreferrer">Link to the hook in the documentation</a></p>