If you use a bad scene key, Phaser just ignores it. IMHO this is not super helpful, so
const { getScene } = Phaser.Scenes.SceneManager.prototype;
Phaser.Scenes.SceneManager.prototype.getScene = function (key) {
const result = getScene.call(this, key);
if (!result) throw new Error('No such scene: ' + key);
return result;
};