On Version 10, this check box has been deprecated, but there are new options on the menu displayed when you click the “>” button by the Find drop-down list box (in the Find dialog box). In this menu, three options available: “Selected Text”, “Word at Cursor”, and “Custom”. After selecting one of these, you can select “Save as Default” to save this option for the future.
I hope this helps. Please let me know if you have any questions.