TYVM for posting.
I first tried Onyx and did all the cleaning it was possible to do.
But the ghost phone was still there.
Then I located com.apple.bluetooth.plist in /library/preferences (made a copy of it in the desktop) and trashed the original file before restarting.
That deleted all my paired Bluetooth devices in System Preferences > Bluetooth and emptied the list of devices from the Status Bar Bluetooth icon menu.
Thank you very much. A bit overkill but I will gladly repair each device instead of having that ghost device there.