ENTIRE FOLDER...VANISHED!!!! Windows 10

You probably moved the folder to some other folder
Windows search sometimes doesn't show what you're searching
Install Everything
On Everything insert a file name that was on the deleted folder. If it is on the computer it will find it. Right click on it and select open path.

First off, it's quite likely that the files are in another folder or in the Recycle Bin. By default, Windows "deletes" moving to the Recycle Bin and prompts for confirmation. The direct deletion with Shift-Del is also prompted for confirmation as indicated.

I suppose there aren't quick shortcuts for hiding files (like in attrib +h) or other exotic things. Recently I nearly deleted C:\Program Files (x86) for imprecision with the mouse, the confirmation prompt (that got stacked and stuck in the taskbar along with the one of other deletion) saved it and my Windows install. I hate it when these or other prompts (like UAC ones) get stacked in the taskbar instead of straightly presented, inmediately or seconds afterwards. You've said the lower left. In the lower right of keyboards for desktop computers there's a dangerous Enter key, the lower left is harmless in these keyboards (at least respect to this problem).

Do you have several drives, or one drive with several partitions? Was C: (or the Windows drive) the accident's partition or was it a not Windows Drive (usually called a data or backup drive). In the latter case, the chances that it hasn't been overwritten are very high. If it happened in the Windows drive, the chances are a lot less, but there're things that can be done. First, stop writing on the drive. In a Windows drive this is impossible unless Windows is shut down. Second, use recovery software, I only know Recuva, but use a different drive to install it or use a portable version ( Download Recuva Portable - free - latest version ). There're alternate ways to boot that can run "small" versions of Windows w/o writing or w/o writing a lot in C:\.

In data partitions, Recuva has found here files deleted months or years ago (in which I'm not interested normally). It indicates if the files have been overwritten or are recoverable (such ancient files normally are overwritten). What I'm suggesting is using the Recuva list to see if the files have been deleted or not, and if so overwritten or not (it wouldn't be a "for sure" method in a Windows drive, but if I don't feel like fiddling with WinRE, installation disks and such, at least I'd boot up Windows normally and use Recuva in C:).