pled on "zpMobile theme : adding gets Uncaught ReferenceError"

Hi,

I upgraded to Zenphoto 1.4.9, and selected the zpmobile theme (for the responsive design). So far so good...

Now I am trying to add an external link into the theme to be able to get back to my wordpress theme.
zenphoto url : http://pled.fr/zenphoto
wordpress url : http://pled.fr/

I added the following code into the jqm_printMenusLinks() function (or in index.php before the call to that function):

Retour au Blog

It displays fine as a new button as expected, but wherever I click on it, I get some "Uncaught ReferenceError $ is not defined" (where $ in one of the functions used by wordpress). Error is raised by jquery.js.

I am not a developer, so pardon me if this is stupid. But is there a way to add such a link properly into that theme ?

Thank you,
pled