So the plugin is working, and it's using the right theme. But the settings page never shows the right theme selected. In the settings page source code it shows that every theme option has a blank "selected" field and the last one on the list is always showing in the dropdown even if I have just saved another one.
If it helps at all, I have successfully used this to show the right dropdown item:
This somewhere in the function:
$options = get_option('option_name');
Then this goes inside a foreach loop for whatever I'm cycling through:
if ($options["name"] == 'current_item') $selected = ' selected="selected"'; else $selected = ''; echo '<option value="current_item"'.$selected.'>current item</option>'."\n";