That's a rude and somewhat inaccurate response.

Photoshop has autosave that works well, even for files with hundreds of layers, so it can be done. That being said, I can see that it's less useful when someone chooses not to save.

As for export, a single-layer file should be considered saved when one exports to lossless. A multi-layer file needs a different prompt, and I note Gimp has that now. It flags the file as "Exported to xxxxxx.png" in the Quit dialog.