Performance :: Strange Massive Deletion Of Files

I encountered a very strange problem last night. A bit of backstory first:

This is my second 'reset' of Windows 10. My first attempt to update into W10 went smoothly for about 1.5 months, then I got a black screen that looped continuously and would not get past startup. After trying many solutions, I figured the installation was corrupted, and started anew.

Everything on this incarnation of W10 has been fine, for about a month. However, last night, something VERY STRANGE occurred. As I went to switch the video I was watching in VLC, I double-clicked a video to load into VLC. VLC changed the video, but my PC lagged for about 20 seconds (unusual for my PC to lag at all). When it stopped, I went to look at my desktop, which is on my first monitor (second monitor has video playing on it), which was previously covered by full-screen explorer to look for the video. I was extremely surprised when I noticed that every. single. icon. was gone from my desktop, except the folder that housed the video I picked to watch.

The only things left were the Garbage Bin and that folder. I figured they went into the Garbage Bin on mistake. Checked. Nothing.

Long story short, after I went into 'My PC' to look in other folders, I was utterly baffled to notice that 400 GBs of data had been deleted from my computer. Yes, everything that was on my desktop (massive amount of videos, games, etc) were gone. Simply.. deleted.

After looking EVERYWHERE for the files, included my Program Files, Windows.Old, etc, and realizing that the items had not only been deleted, but REMOVED FROM PROGRAM FILES in many instances, I did a System Restore. Unfortunately, this did nothing except restore the FOLDERS, as the files themselves are still gone, and the 400 GBs is still missing.