C drive filled up when moving from an SSD to network drive

I have a separate SSD on my motherboard (Drive E) that I was copying a folder with a over 80 gigs of files on over to an HDD on my network (that has a few hundred Gigs left), when it said I needed 35 more GB at the start of the operation, I thought this strange and hit ignore.  It started transferring but hit a point where it couldn't transfer any more data.  I noticed then that it C drive was red, meaning it had filled up my C drive instead o.0.

Is there a folder somewhere I can browse to and delete files (like a temp folder or something?)  because I had over 30 gigs free before this.  So it's somewhere on C drive.

There were no files ultimately copied to my network drive from this original operation.

I tested a theory, and when I move a smaller, 3 gig file it transferred it to the target folder completely and can be found via browsing to said file on the network storage.

What happened here?  I'm new, so obviously I missed something and shouldn't have ignored the space needed warning but... I thought it just wasn't reading the room left on my network storage drive properly or something.  I was wrong.