So I tried to take a screenshot today, but I couldn't find it. I had previously set a setting that saved my screenshots in a specific place. It took about an hour for me to figure out where they were going.
(I was slightly thwarted because I was hitting Ctrl-PrintScreen - on my last laptop the print screen button required hitting Fn and I got confused. Ctrl-PrintScreen puts the screenshot into a paste buffer.)
So after finding out where the screenshots were going I tried to set the setting again to get the screenshots to once again save in the correct place.
Things like this shouldn't happen in a modern polished Linux Distribution like Debian; but the popular belief is that there are a lot of volunteer programmers who work on Linux, so mistakes happen, because they aren't professionals.
That's not the case here, check out the webpages linked below. These are small people who have the power to help, but are too focused on maintaining their power over their little corner of the operating system. They refuse to communicate effectively; or solve a problem that many users are having.
After doing a bit of research, there are a few ways to fix it and make it work again. Users shouldn't be expected to go to great lengths to change a setting... I may give this more consideration later and see if I can unravel this web of garbage; but I have to work in the morning, I need to sleep now.
Relevant pages:
https://askubuntu.com/questions/114429/how-can-i-specify-the-default-save-directory-for-gnome-screenshot
https://bugzilla.gnome.org/show_bug.cgi?id=699642
https://cialu.net/how-to-change-default-gnome-screenshot-savings-folder/
https://help.gnome.org/users/gnome-help/stable/screen-shot-record.html.en
https://unix.stackexchange.com/questions/279985/how-do-i-change-the-location-where-screenshots-are-saved-in-linux-mint-17-cinnam
https://unix.stackexchange.com/questions/279985/how-do-i-change-the-location-where-screenshots-are-saved-in-linux-mint-17-cinnam
https://wiki.debian.org/ScreenShots
https://forum.manjaro.org/t/gnome-change-default-screenshot-location/67834
https://forums.debian.net/viewforum.php?f=6&sid=96b34c5e3e27354cd0582ff268e79c68
So you can install custom scripts in your home directory. You can disable the six included shortcuts and make new ones pointing to a different screenshot program, you can install a 3rd party "Gnome Shell' extension, or. apparently there is a way to do it with systemd user units??? But you get the idea...
Petty bickering has removed this feature for millions of people.
Linux Sucks!
But at least you can fix it, if Microsoft doesn't want you to take a screenshot you simply won't be able to.