Sequence deleted after closing - auto save files empty

Hi everyone, 

I recently created a new sequence to try to replace some existing footage in my main project. Everything seemed to go ok (even though it seems this should be more seamless in general, but that's for another day) but I accidentally 'X'ed' out my sequence in the timeline panel and when I reopened it, everything was gone. I imported multiple autosave files and they are all blank. The sequence is saved, but all the assets are gone. Anyone know what I did wrong? Thankfully, I already copied the files into the main project, but for future reference, what in the world? 

Thanks in advance.