[Plugin: MM Forms] Changing success text?

I’m trying to change the “it worked!” text when you input a form from “Form data saved successfully. Thanks for submitting!” to “Thank You! We will contact you shortly!”

I’m making the change in mm-forms.php, on this line:
case ‘mail_data_saved’:
return __(‘Form data saved successfully. Thanks for submitting!’, ‘mmf’);

This successfully changes the text upon submission, but the AJAX functionality doesn’t hide the form … the success message appears underneath the form fields.

I haven’t been able to find the “form data” text anywhere else, so I’m not sure exactly what the problem is. And I can change the text slightly, adding in a typo/mispelling to one of the words, and it works as intended.

Any idea what’s happening here, and how to fix this?

http://ww.wp.xz.cn/extend/plugins/mm-forms/