how do i - include the items without a facet

[Jonathan Vanasco]

My result set for a query has 451 records
293 of them do not have a value set on 'facet.location_name'

how can i specify searching for these items?

i've tried:

        fq=facet.location_name:""

and based on 
http://wiki.apache.org/solr/SimpleFacetParameters#head-b618fc041ffc0c26ea45bdf086895e5b87061bd4

        fq=-facet.location_name:[* TO *]
        fq=facet.location_name:[* TO *]

but none seem to work