custom payment gateway problem

I hope anyone can help me with a problem we have with a custom payment gateway, i am trying to figure out where in the theme i can locate the code responsible for the item status. If a member pays for the item and we receive the callback and the member goes to his buyer history in his account then clicks on the view listing button he gets redirected to page not found.

When i use the admin test callback and user goes to the buyer history the item shows leave feedback and if the member clicks on the leave feedback button it directs him to the right page where he can leave feedback

im just looking for the files where this code can be found to change the status of these items so members can leave feedback after purchase of item so they dont get directed to 404 error page

thanks