Location of user account / profile photo

Thanks. That's good news. I incorrectly assumed the screenshot was of a blank image because you had already deleted the image you want to retrieve.

Assuming the picture in that Users & Groups pane is really the one you want to retrieve, then do it this way using Terminal:

dscl . -read /Users/john JPEGPhoto | tail -1 | xxd -r -p > ~/Desktop/pic.jpg

That will perform a hex dump to deposit a .jpg of your login picture on your Desktop, named pic.jpg

It would be best to copy that line (triple-click to select the entire line), paste it something like TextEdit (for example), substitute your "short user name" for "john", and finally paste the result into Terminal.

It is stored as binary data in Directory Services, and can be retrieved from there.

Is it still your login picture? Because the bad news is that if you already changed it to something else, it's gone.

If it is still your login picture you can export it to an openable .jpg file. Write back for instructions.