Well it would be strange to use URLLoader with HiddenSearch. I think what you mean is using URLLoader with the Search module.
There are a couple problems with this configuration, and I think you should check out the Sideview Utils documentation a bit more. You're using ViewRedirector here instead of Redirector, and using HiddenSearch instead of Search.
But in a nutshell URLLoader takes the arguments from the URL and makes them available to all the modules downstream (ie nested inside URLLoader). So for example you would put a Search module downstream from the URLLaoder, and then you put $event$ somewhere in its 'search' param.
But the documentation goes into more detail than this and provides several examples.