Open the view and make the theme with the labels active.
Switch directly to the script windows and click the Run button.
This code returns the coordinates of the first text graphic in a message box. You can modify the script to loop through all labels attached to a theme and to populate fields in a table with the values.
The auto-label process anchors the lower left corner of the text at the polygon centroid. The first and last method will yield different results if you use the default lower left text placement option in the auto-label.