Backup question

Here's how I backup my files. I'm very disciplined about where I keep all of my files - audio, video, project, etc. - they all go in the same project folder. So all I do when I back up is copy that entire project folder.

But it occurred to me that there might be files in use in my project that are not in my project folder. Not intentionally, but I'm sure I forget to move files into the project folder from time to time.

Is there a way to make sure that what I've backed up contains every piece of media that's in the project while retaining my original file/folder structure?