title: Unbind can't find model that clearly exists
body: <p>I'm trying to do a query on a model called uploads, where I search for all uploads that have a given tag. I am using the CakeDC Tags plugin, and I am working from this tutorial, <a href="http://mark-story.com/posts/view/using-bindmodel-to-get-to-deep-relations" rel="nofollow">http://mark-story.com/posts/view/using-bindmodel-to-get-to-deep-relations</a>. I am trying to overcome the fact that plugin provides two queries (which cannot be searched) by default. </p>
  
  <p>So, I am attempting to do a join via the bindModel function: </p>
  
  <pre><code>$this-&gt;Upload-&gt;Behaviors-&gt;load('Containable'); 
  
      $this-&gt;Upload-&gt;unbindModel(array(
          'hasAndBelongsToMany' =&gt; array('Tag')
          ));
  
      $this-&gt;Upload-&gt;bindModel(array(
          'hasOne' =&gt; array(
              'Tagged' =&gt; array(
                              'className' =&gt; 'Tags.Tagged', 
                  'foreignKey' =&gt; false,
                  'conditions' =&gt; array('Tagged.foreign_key = Upload.id')
              ),
              'Tag' =&gt; array(
                  'foreignKey' =&gt; false, 
                  'conditions' =&gt; array('Tag.id = Tagged.tag_id')
              )
          )
      ));
  
      $tag = $this-&gt;Upload-&gt;find('all', array(
          'contain' =&gt; array('Tag'),
          'conditions' =&gt; array( 'Tag.name' =&gt; $tagname)
          ));
  </code></pre>
  
  <p>However:  SQLSTATE[42S22]: Column not found: 1054 Unknown column 'Tagged.tag_id' in 'on clause'</p>
  
  <p>I believe that this might be because Tagged is just a join table, and not a proper model.
  How can I get the table to join as I need it to? </p>
  
  <p>The SQL dump: 
  SQL Query: </p>
  
  <pre><code>SELECT 
      Upload.id,
      Upload.name,
      Upload.description,
      Upload.created,
      Upload.modified,
      Upload.filetype,
      Upload.numberofviews,
      Upload.numberofdownloads,
      Upload.model_dir,
      Upload.model,
      Upload.owner,
      Upload.license,
      Upload.category,
      Upload.default_picture,
      Upload.soft_delete,
      Tag.id,
      Tag.identifier,
      Tag.name,
      Tag.keyname,
      Tag.weight,
      Tag.created,
      Tag.modified
  FROM
      database.uploads AS Upload
          LEFT JOIN
      database.tags AS Tag ON (Tag.id = Tagged.tag_id)
  WHERE
      1 = 1 
  </code></pre>