I have read every word of this thread.
I chose "forget this device" so my UE Roll (AWESOME) portable Bluetooth speaker could pair with someone else's cell phone. Now my iPhone 6s Plus will not recognize or pair with the speaker, when I put the speaker in pairing mode, while the iPhone searches to discover any nearby bluetooth devices.
I tried the suggestion on this thread, holding down the + volume button and the power button for 10 seconds, while in pairing mode, and while not in pairing mode.
I also tried a soft reset. I did the latest update to to OS. I did everything I could think of.
I read in a different thread that when an iPhone refuses to re-discover a Bluetooth device, a hard reset from the Setup menu has to be done to the iPhone, which causes a factory reset (but does not erase any stored data on the iPhone). I also read of people who did such a reset with no results but all the headaches of having to restore personal preferences that get erased.
I appreciate your help so much!