These days most demo models are physically stripped of features like Bluetooth, it isn't left behind; they do that to keep someone from blasting their Soundcloud mixtape over the speakers in the store. No firmware is going to bring this back.
Samsung and Google do similar thing; Samsung strips the IMEI# from demo phones, google puts S/N tied MDM on it so it can't be used and if you manage to reflash it then the MDM will still be present nor will they remove it.