searches and searches and searches but doesn't find anything.
I don't know enough about bluetooth to know how to fix it, but I can tell you what I did to break it: After upgrading to 13.10, I noticed that the bluetooth icon was no longer in my top Unity panel. So I ran:
and, like magic, there it was and I went along using my bluetooth headphones without a care in the world.
gsettings set com.canonical.indicator.bluetooth visible true
...until a couple days ago. I did the simplest thing in the world to break it. When you click the bluetooth panel icon in 13.10, the very first drop-down option is something very cavalierly called "Bluetooth" with a little check mark beside it. I must've flinched at the wrong moment or something because SOMEHOW I managed to uncheck "Bluetooth" and, like that, my whole world came crashing down. The icon immediately disappeared from the panel (though that was simple enough to bring back by repeating the above code + restart) and now any scans for bluetooth devices comes up with absolutely nil.
I've tried all kinds of restarts and turning bluetooth on/off a couple dozen times in the settings GUI.
I've even tried repeating what I did to break it as if the reverse-amnesia theory applied to computers. Any ideas would be greatly appreciated.
$ restart bluetooth
restart: Unknown job: bluetooth
$ hcitool dev
$ hcitool inq
Inquiry failed.: No such device
$ hcitool scan
Device is not available: No such device
Oh, and I'm also running a triple-boot system with OSX/Ubuntu/Windows and the bluetooth works fine under the other OSes, so I don't think it's a hardware problem.