Clips mostly removed from timeline

I have been working with Final Cut Pro for about a month. I imported a project from iMovie into Final Cut Pro that has two hours and a quarter of demo audio for a sung-through musical with a clip of an empty stage through the whole thing and titles describing the stage directions and other pertinent information. I decided I wanted to do better than that so I got the storyboard application Previs Pro and have been generating from 30 to 50 clips per song showing the settings and the action on stage. As I learned more I doubled back to improve what I had done. As I was working on the first song I discovered, to my horror, that at some point all of the jpeg clips for the other songs had been removed from the timeline. Using undo I managed to get about half of them back, but the rest must have been removed during some earlier session. I didn't know enough to have enabled backups. This is a major disaster. A lot of work vanished. -- Is there any way to recover, or do I have to go through reinserting the clips. -- Also, is there a way to set it up so that everything stays linked to the audio? While I am working on one song I don't want any of the clips associated with the other songs to be touched in any way. I want them to stay put. They belong with their audio. I especially don't want them to get knocked off of the timeline.