Protecting plugin styles with Child theme

I was under the impression that if I placed a plugin folder containing a modified stylesheet for a plugin into my child theme, that WP would look in the child theme folder first and use the stylesheet in that folder. Am I mistaken about that?

I’m using a child theme on the genesis framework, but I’m not able to get my slider plugin stylesheet in the child folder read. Hate to modify the core and lose it when I update the plugin.

Can someone help with this?
Thanks very much
Bill