Sitemap page search on nested single pages broken?

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Before I report a bug....

I have this structure:
Home (normal C5 page)
        Admin pages (single page installed from package)
            Admin page 1 (single page installed from package)
            Admin page 2 (single page installed from package)
            ...
    Other pages
    ...


When I go into page search, select Parent Page and set it to 'Admin pages' and search all children it returns nothing.

Did I miss something or is this a bug?

surefyre