Preserve external link on featured image on a post

Hi,

I used custom fields to give my featured images an external URL. You can see how this works on my site here:

http://brewspotting.com/

When I installed WP Touch, it stripped featured image external URL. Is there a way to preserve this function while still using this plugin?

Thanks for any help in advance.

SB

https://wordpress.org/plugins/wptouch/