I accidentally deleted some styling in CSS custom inserts. Using Atahualpa 3.6.1. I contacted my Host to restore the file, yet it didn't fix the CSS issue. I also have a recent backup on my own computer. Was going to try to restore the css file on my own, however, I can't seem to find the right file. I found the css.php file but the custom code was not in there. Which file should I upload to the site? Again, a total restore didn't fix the css issue.

Thanks.

the CSS insert is an option of the theme and it is stored in the database. restoring theme files will not effect this. You would have to do a database restore to get the values back.