I was trying to deselect the middle band (roughly 4:00 mark), and I think I hit alt-b or shift b-something, then mostly everything disappeared. Control-z wouldn't fix it. If I go to dev view, I can still see everything.
I've attached a video, any ideas what happened?
https://drive.google.com/open?id=1DnxHwMBb4aoAJXoLnQTDN2dgSD0Nxk1y
jjjblender try hitting alt - h and see if everything comes back. I think you hit shift-h and hid some of your mesh.