Duplicated cut has disappeared from project...

Hey everyone. Brand new to these forums. Been cutting a project on FCPX for several weeks now. My usual work flow is to duplicate the project every once in a while in order to preserve progressive "drafts" of my cut. This works well for me. Until my most recent attempt. Several days ago, I duplicated the latest cut and began further refining my edit. I finished for the day and revisited my cut today. But unfortunately, the most recent version of the project is completely absent along with all the work I did. Additionally, there's an "exclamation point" sign over the event folder containing all my various project drafts. Has anyone ever experienced this? Trying to figure out if there's a solution.

Running FCPX 10.2.2 on MacBook Pro with Retina display, OS X Yosemite (10.10.5)

Thanks