In my case, my phone stops seeing BT devices every now and then (maybe once or twice a week). A workaround is to either toggle the phone to flight mode and back, or just toggle BT off and back on. Somewhat annoying, but at least easy to work around when needed. I've been seeing this for a long time, probably since 8.1 update.
A minor correction to my post; this happened to me today again and just toggling BT off and on wasn't enough, I had to toggle to flight mode and back.