Connecting to Bluetooth earphone disables keyboard
I think the problem is, the way the device was manufactured, as a physical keyboard. Problem is, in that moment, your "keyboard" are the bluetooth earphones, and it is considered as the default keyboard. That's why you cannot see anything.

What you can do is, go to bluetooth configuration, and you will see your headset. There should be a gear icon or something to access to configuration for that bluetooth device. THere, you can disable or enable media audio and phone audio, it should show something like "Input device", just disable that. That should disable the device as a keyboard.