In current raring, when the bluetooth antenna is disabled the bluetooth indicator icon is missing. This is a problem because the bluetooth indicator is the *only GUI interface* for enabling the bluetooth antenna when it's soft-disabled. So you can disable bluetooth in the indicator, which makes the indicator itself disappear so that you can never re-enable it.
ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: indicator-bluetooth 0.0.6daily13.02.19-0ubuntu1
ProcVersionSignature: Ubuntu 3.8.0-6.13-generic 3.8.0-rc7
Uname: Linux 3.8.0-6-generic x86_64
ApportVersion: 2.8-0ubuntu4
Architecture: amd64
Date: Wed Feb 27 04:56:48 2013
InstallationDate: Installed on 2010-09-24 (887 days ago)
InstallationMedia: Ubuntu 10.04.1 LTS "Lucid Lynx" - Release amd64 (20100816.1)
MarkForUpload: True
SourcePackage: indicator-bluetooth
UpgradeStatus: Upgraded to quantal on 2013-01-25 (32 days ago)
There is some workaround to re-enable BT?
I tried from system setting -> hardware -> bluetooth but I cannot enable BT anymore