Did I Just Lose All My Changes?

I'm brand new to Calibre. I imported a book as a MOBI and was editing it (It was a scan and there were lot's of spelling errors). I corrected all the spelling errors, adding proper headings, added a table of contents for 55 chapters.

I saved every single file as i was editing over a few days. Once finished. I closed the book editor and clicked "Convert". I converted it from MOBI to EPUB... and all the changes appear to be gone in the viewer. Is there any way to recover my changes? What did I do wrong?