On the lines in showcat.php after get_thumbtmpl you even assume that what you're showing is a product:
Content visible to verified customers only.
IMHO the code in showcat.php should be:
$catimage = get_thumbtmpl( $id, $thumbrc, $height, $width, $checklink)
There's no need to pass $pcat, it's not a category, it's a product thumbnail.