[Plugin: prettyPhoto Media] no thumbnail when LIKEd on Facebook?

Hi there – love the plugin layout! But unfortunately it won’t attach a thumbnail when I hit the facebook Like button on a certain image.
In fact Facebook Like button shares the whole gallery URL instead of the single image. The Twitter button works fine and it shows a link like:
http://example.com/pagename#prettyPhoto%5Bgallery-134%5D/1/

I found the code where the facebook and twitter mark-up is located (prettyphoto-media_settings.php)and was wondering how to correct that:

$facebook_markup = ‘<div class=”facebook”><iframe src=”//www.facebook.com/plugins/like.php?href={location_href}&send=false&layout=button_count&width=450&show_faces=false&action=like&colorscheme=light&font&height=21″ scrolling=”no” frameborder=”0″ style=”border:none; overflow:hidden; width:50px; height:21px;” allowTransparency=”true”></iframe></div>’;

thanks!
g

http://wordpress.org/extend/plugins/prettyphoto-media/