It uses a form post for the search, so passing a value in the URL would have never made a difference.
I've updated the search page to save the submitted form in the session. Then I added code on the results page to restore the previous search when ?return is added to the url.
Then I added a "return to results" link on the edit_option.php page with the added url parameter to restore the search.
Then I updated the link on the edit_order.php page to go back to the results page and add the necessary url parameter.
Then I updated the edit_charges.php page and noticed that there are two results pages that link to the same page, so I had to update the url from the edit_options.php page to pass the correct return page url to this page so that I could redirect to the correct results page based on where the user came from. Then I updated the edit_charges.php page to detect the correct page based on the url parameter and redirect accordingly.
I'm sending you an invoice for 30 minutes of work.