I've been looking into this for a little while, and my conclusion so far is that there may be something a bit non-standard or unusual about the bluetooth in the Siri Remote / 4th generation Apple TV remote. Certainly it manages to upset LightBlue on my Mac and iPhone in slightly different ways.
If I use bluetoothctl, the remote does show up and I can connect to it (at least if I hold menu+volumeup for 5 seconds whilst bluetoothctl has discovery enabled):
root@raspberrypi:/home/pi# bluetoothctl
[NEW] Controller B8:27:EB:6C:15:98 raspberrypi [default]
[bluetooth]# scan on
Discovery started
[CHG] Controller B8:27:EB:6C:15:98 Discovering: yes
[bluetooth]# agent on
Agent registered
[bluetooth]# default-agent
Default agent request successful
[NEW] Device 78:9F:70:5E:A3:14 DJ7Q6MZ9GQQT
[NEW] Device 67:8F:99:BC:EE:C5 67-8F-99-BC-EE-C5
[CHG] Device 67:8F:99:BC:EE:C5 RSSI: -64
[CHG] Device 67:8F:99:BC:EE:C5 RSSI: -44
[CHG] Device 67:8F:99:BC:EE:C5 RSSI: -64
[CHG] Device 67:8F:99:BC:EE:C5 RSSI: -44
[bluetooth]# connect 78:9F:70:5E:A3:14
Attempting to connect to 78:9F:70:5E:A3:14
[CHG] Device 78:9F:70:5E:A3:14 Connected: yes
Connection successful
[CHG] Device 78:9F:70:5E:A3:14 UUIDs:
00001800-0000-1000-8000-00805f9b34fb
00001801-0000-1000-8000-00805f9b34fb
0000180a-0000-1000-8000-00805f9b34fb
0000180f-0000-1000-8000-00805f9b34fb
00001812-0000-1000-8000-00805f9b34fb
0000181e-0000-1000-8000-00805f9b34fb
8341f2b4-c013-4f04-8197-c4cdb42e26dc
[CHG] Device 78:9F:70:5E:A3:14 Appearance: 0x03c0
[CHG] Device 78:9F:70:5E:A3:14 Modalias: bluetooth:v004Cp0266d0000