It's an easy mistake to have the wrong needles pointing in the wrng direction at the worst time (one on ADF as a leftover from the take off, when on approach both should be on VOR for example). That's why I try to make it a habit in the climb to switch both needles OFF, so that during the approach preparation I have to make a conscious effort to re-select the correct boxes. It's a small silly personal rule, but as I said, it's an easy mistake to make in an automated flightdeck where all the tuning is done via the MCDU.
Anyway, even if you switch them all OFF on the FCU, the SBY RMI is still pointing to your selected VOR/NDB's, so there's your answer without even looking in the FCOM!