Live Demo link :
http://mikaraidesertsafaricamp.com/opencart/index.php?route=product/category&path=18
{Click here for demo
Compatibility: v1.5.0, v1.5.0.1, v1.5.0.2, v1.5.0.3 , v1.5.0.4, v1.5.0.5, v1.5.1, v1.5.1.1 ,v1.5.1.2, v1.5.1.3, v1.5.2 , v1.5.2.1 v1.5.3 , v1.5.3.1 ,v1.5.4 ,v1.5.4.1, v1.5.5,v1.5.5.1,v1.5.6.1,v1.5.6.2,v1.5.6.3,v1.5.6.4

By this module customer can create a list of selected product without login.

This module work like ( wishlist without login )

You can check it in opencart category, product and search page ( Add to shortlist) button

Dont need to change your code, it is very simple