Child rows contained in a subtable are not sortable

I have an application that requires the detail rows to be another DataTable with support for column sorting and filtering. Initially this was implemented with the 1.9.4 of datatables but I could not get the sorting of the subtable to work. I've tried upgrading to 1.10.4 but the sorting still doesn't work.

Config for the subtable is:

{
"data": "movieSeries",
"order": [[0, "asc"]],
"columns": [
{"title": "Title", "data": "title"},
{"title": "Date Published", "data": "date"},
{"title": "# of Pages", "data": "pages"},
{"title": "Movie Release Year", "data": "movieReleaseYr"}
]
}

Data is:

    {
        "series": "Harry Potter",
        "books": [
        {
            "title": "Harry Potter and the Philosopher's Stone",
            "date": "6/1997",
            "pages": "309",
            "movieReleaseYr": "2001"
        },
        {
            "title": "Harry Potter and the Chamber of Secrets",
            "date": "7/1998",
            "pages": "341",
            "movieReleaseYr":"2002"
        }
     }

Subtable is rendered by when a click handler for tr fires. Click handler calls oTable.fnOpen(row, html, htmlClass). HTML for the subtable is below.

But when I look at the event listeners in the chrome web console, the <th> rows do not have a click handler for th.sorting.