i have always assumed that there is only the notification LED beside the proximity sensor. when i woke up this morning, there was a very faint red LED next to the bigger notification LED. i have never seen this before and i didn't know how it turned on or how to turn it off. when i rebooted the phone, it immediately shut off and didn't turn on again. when i looked at the phone closely, there is indeed 3 holes there: the notification LED, proximity sensor, and this LED i'm trying to identify.