My document folder ended up in endnote back up? How/why. No longer usable

My lifes work has been in a my documents main folder and subfolders for 14 years.

I lost it this morning and found it in an old  endnote back up. I didnt use endnote yesterday but it opens with word. I didn’t do a back up.

I know this is slightly off topic but why and how does anyone know?  Is it significant that it was in endnote?  I cant use any of the folders now as they are not recognised bys the system. I did some alterations - bits and pieces of work after yesterdays back up to external hard drive. just little things so would rather the original files back. The main document I was working on has been found and I re saved it. Can anyone help please.