I had rolled back my update a while back and prevented further updates, but I finally had to give in and update, and sure enough, Bluetooth disappeared. So I reset Windows (using the option to retain files but remove all apps and do a clean install) and everything seems to be working properly - in fact, I have to admit that my system is working much better now, oops. However, one still needs to go into the device manager / Bluetooth / Intel(R) Wireless Bluetooth(R) / Properties / Power Management and uncheck "Allow the computer to turn off this device to save power", otherwise Bluetooth devices will freeze periodically.
