URL Param passing compatible with domain-mapping

I'm looking for a way to pass a parameter in a URL that is compatible with the domain-mapping plug-in.

For example, something like Jeremy Shapiro's URL Params plug-in that gives you a Short Code to grab any URL Parameter would work. But, it appears that doesn't work with domain-mapping or possibly multisite.

Specifically, I would like to be able to pass a parameter like this:


and be able to get to the value of 'rid' (referrer id is what this is). When I install Jeremy's plug in, I don't see it in the children sites of the multi-site setup -- only the top level wp.xplain.com