I’m the PlugIn author that wrote Car Demon. I just wanted to pop in here real quick and share a little information on the problem and the ‘solution’.
The issue causing his problem was caused by the theme. In their functions.php file on line 41 was this line
add_theme_support( 'post-thumbnails', array( 'post' ) );
That line is overwriting the featured image / thumbnail support for all custom post types and is explicitly allowing the feature only for ‘posts’.
The quick and dirty solution was to change this line to;
add_theme_support( 'post-thumbnails' );
This allows the feature for all custom post types. Obviously editing the theme directly can cause an issue if the theme is upgraded in the future, but it is the only solution I could come up with.
Long term I think the solution is to have the theme developer take a look at line 41 and make changes as needed.
