Resurrecting an old thread, my bluetooth settings all vanished yesterday, and turning off and on the bluetooth power did not restore them. It took a reboot. First time that's happened to me since I've had the phone (April 20).
This seems to be a pattern: things degrade over time. Either the GPS won't get a fix, or Wi-Fi Calling won't connect, or the browser gets very slow, or now the bluetooth settings vanish, and a reboot makes things work right again. This smells a lot like a heap management bug to me -- corruption, or fragmentation, or leak. I hope things are better after the Gingerbread/bug-fix update that's supposedly coming soon.