This is certainly a less convenient approach. You always need to parse the class name in your head to open the correct file.
And, yes I understand that you can have grep output a path name and pass that directly in as an argument to your text editor. Similarly, it'd be relatively trivial to write a bash function that'd parse the class name and find the correct file to open.
Something like:
function lookupcss() {
find . | grep $(expr "$1" : '\(.*\)__.*' | sed 's/_/.*/g')".*\.css$";
}