However the hint of getting a SMS is too short and not quite obvious, better to flash a little longer
I hear ya! The original intent was to try and make the player have to pay attention to it, but I can understand it can be a very frustrating thing to miss so I'll look into adjusting it in a future build. In the meantime, there is a sound effect that plays as well as the flash, so keep an ear for that if you're able to!