Vadi on "[Plugin: W3 Total Cache] "js file doesn't exist" error - but it really doesn't exist"

This sort of error message pops up every now and then?

Recently an error occurred while creating the CSS / JS minify cache: File "<snip>/wp-content/themes/Memoir/js/custom.js" doesn't exist.

However, such file really doesn't exist - neither on my web server nor in the theme files. Where is it pulling the name from?

http://wordpress.org/extend/plugins/w3-total-cache/