Flashing a light when a circuit breaks
You make some sense. Assuming that by 'flash' you mean the LED to be on continuously, your circuit could be







simulate this circuit &ndash; Schematic created using CircuitLab

A disadvantage is that while the switch is closed the full LED current (and even more) is always drawn. To prevent this, you can use a transistor that can be 'enabled' by a current that is a few orders of magnitude lower than the LED current:







simulate this circuit