Where is the "Shift Cmd Ctrl 3" default location?

If you do include the Control key (Shift-Command-Ctrl-3 or Shift-Command-Ctrl-4), then the image goes to the Clipboard instead of being saved to a file on the Desktop. You can see it there via Finder>Edit Menu> Show Clipboard, and you can paste it into a document, such as into Preview (via "New from Clipboard) or into a Mail message.

Default is the Desktop.

Do a Spotlight search (magnifying glass in the upper right) and type in "screen shot"

If it's saving them at all then it will show up there and you can just do Show All -> Search to "File Name" -> Find the file and where it's being saved to.

I assume you're wanting to take a screenshot? If so it is Command+Shift+3. Don't hold down Control.

You can also do Command+Shift+4 to do an area selection or Command+Shift+4 and then press the Spacebar to do specific windows.

jsd2 got it! Adding shift to any screenshot command-ctrl-3 or 4 or 4 + space will send it to the clipboard.