Almost pulled my hair out again. Need help with Backing Up images

Did you try to do a search for *.cr2 on your hard drive?
Sometimes I have put images in the wrong folder by accident.

I always copy from the media not move.
Check that the files are on the hard drive
Re-format in camera afterwards

Personally, I used syncback for years without issues. You can have it automatically do backups at specific times of the day/week/etc. I don't completely trust it, as I do check that it's actually doing its thing from time to time.

But really, the best thing is to use RAID which can configured for data mirrorring in real-time, or "protecting" the data with error correction codes on other drive. This will set you back a few hundred dollars, it's the only solution IT pros uses.

Your photos may not actually be gone. Maybe only the "directory" pointers to the data itself. There are data recovery tools that may be able to recover your "lost" data.

Have they been made 'hidden' files by some quirk? - Turn on visibility of hidden and system files.
I'm not sure if doing a search with this turned off will find them if hidden or system.