I can't locate my original zipfile to update

I bought a second hand ecommerce website which was launched 2 years ago after a website developer amended it. I no longer have contact with the developer.I use Wordpress and Woo commerce. I have an X Store parent version 4.3 and X store child theme 8. version 0.0.1 I need to update the site as I have lost my navigation bar and wonder if it’s because the theme is an old version. How can I locate the original zip file so I can ask a WP expert to update it? I’m scared of breaking the site if I do it. But customers can’t navigate my site atm so it’s a bit urgent that I get this fixed! Can anyone help please?