I had a similar situation when collaborating with a team on a video project during a high school internship. Somehow I managed to delete the entire timeline accounting for hours of editing work that my boss had put in. To this day I don't know how it happened, I just looked down and all the clips were gone from the timeline. In the end, I think we found some semblance of a backup, and at least we didn't lose the raw data/video content, but I can relate to the out-of-body experience that hits you when you realize you just royally screwed up your team's progress and there's nothing you can do about it.