I found this thread because I had the same problem. Extremely mystifying… everything’s fine, auto-save is working fine, I saved everything, turned off the computer, and added some RAM. I turned it on, RAM showed up fine, opened the project, and the sequence was completely gone. The craziest part was that it was completely gone from all the auto-save files I checked!
I could create a new sequence, but the original was completely gone. I’m 99.999999% positive I didn’t accidentally delete it in the process of saving and closing down.
Here’s where it gets really weird… I wasn’t ready to tell my wife (the editor) that she had just wasted 4 very valuable hours of editing while the kids were with a babysitter, so I decided, based on something I read here or somewhere else, to open every single project file in my project files folder.
I actually found the missing sequence inside a project file that had not even been open at the time, and hadn’t been opened in months!
I’ve always been annoyed by how FCP opens all the previously opened projects when I start the program–maybe it’s a setting I missed, but I’m 99.9999% sure that project was not open while she was working on the current project.
I couldn’t believe it, but I’m not complaining! 🙂