It was too big to fit in the recycle bin so it was permanently deleted. And I did restore them to an external device. And I deleted the folder months ago, perhaps half a year ago by now. The files are undamaged, but I opened up a paint.net file in notepad++ once and saw that there was an XML document built into the pdn file, and there was a thumbnail ID which was in base 64, except in the un-openable files, the ending quotation mark and > were missing and I don't know where to put them. I'm convinced that all I need to do is find the right place to put those two characters and then the file will open.
The partition I recovered the files from hasn't been touched since I deleted the files.