Try to open the file on a different way, from "recent files", or from explorer.
Or maybe you just have to try to open it a second time.
I have experienced this issue also several times, but I can't remember the exact abouts.
Can anyone provide an update on this? I recently had been working on a project over several days and saved it every hour or so. I went to open the file the morning, and everything is gone. The file is still in the folder, but when I open it, everything is gone. I had several layers and made a few blocks while working on it, but none of it is there. I've tried autozoom ("za"), but it still won't show up. Please help!