[edited by: keyplyr at 6:49 pm (utc) on May 28, 2017]
not2easy
6:21 pm on May 28, 2017 (gmt 0)
If you got the theme from the WordPress Themes repository, you can just reinstall the theme. If you got the theme somewhere else, you would need to get a new .zip file from the company.
I would be hesitant to use a theme that is not available from the WP Themes repository as there is the possibility that the theme may be old, not supported or even compromised.
ergophobe
7:50 pm on Jun 15, 2017 (gmt 0)
In general, regardless of where you get the theme, you'll want to create a child theme and your style.css file would be there anyway. I'm not sure what happens if a parent theme is missing the style.css, but you are using the child theme.
PS: Why use a child theme? Because that way you can implement updates to your parent theme without losing your customizations
TorontoBoy
7:42 pm on Jun 30, 2017 (gmt 0)
StanleyWP is NOT part of wordpress.org's themes library and is therefore not tested by Wordpress.org. The theme is a version of the bootstrap theme, and is over 3 years old, so you need to ensure it is still maintained.
The styles.css is there. Use at your own risk. If your theme does not come with styles.css, just create it using any text editor and put it into your wp directory.