No easy way to scrape that with Full-Text RSS at the moment. It’s important to look at the source HTML to verify the element you want to target was actually served up as part of the main HTML response and not, as in this case, inserted after Javascript execution. One easy way to do that is to use our Site Config creator to load a page: http://siteconfig.fivefilters.org as that will ignore Javascript. Alternatively you can disable Javascript in your browser temporarily and then use the Chrome developer inspector.
In the future we’ll have an option to allow users to have extraction occur on pages after JS has been executed, but no estimate as to when that will be ready.