Icons mysteriously disappear

Hello,

On the homepage i managed to change the icons to my choices from http://documentation.hb-themes.com/icons/
But using the visual edit composer to access the icon name and change it, in other pages has resulted in the icon totally disappearing.
I do not have the plugin gridgallery, like i noticed in other question, so i do not know what is the source of interrupting.
Is there a way to by pass or solve this issue?