Bluetooth not available anymore
Here is the list of all Apple BT symbols and they meaning.



Additional steps:

Log in as different user to see if it is your profile related.

Start in safe mode to see if other applications are making problems

Since you have another major problem with missing BT in sys pref, resetting SMC and PRAM might help.

Use Manual method to ON/OFF the BT

Type Bluetooth in Spotlight

Select Application- Bluetooth Exchange

will bring up a switching window



Last not least, reinstall your OS.