Cal here from Shopify, thanks for reaching out to us. You may need to download a fresh copy of your theme and replace the current theme you have published entirely. When you delete a .liquid file, it's gone forever. Were you using a free Shopify theme?
You can reach out to the theme developer, and request a fresh copy of the theme. You can explain the accident to them. You will find their support information on their theme page in the theme store.