As far as I know, it'll be the same as a '93 I got my header panel out of had the same bezels as my '90, so I'm gathering the '94 is about the same?
The short answer it sounds like either the foglight switch or rear defroster switch.. Look at the back of that bezel panel. Does it have two holes for switches? [Pics always help if you have].
The long anwser, if you have all of them installed, you'll have on the left, headlight switch, then fog light and finally defrost closest to the steering column. On the right working outwards, you'll have transmission power switch for auto [It's been said on here somewhere that with the '91's going HO the did away with that one], then you have the rear wiper switch, then the next panel is the 12v accessory/cigarette lighter.
Now depending probably on what parts were available, where the XJ was assembled, etc, you can have two different style bezels on them. The back is the same, but some have a the unused switch hole covered by the thick plastic front they put on, and some have just blanks put in.
Check your XJ's manual, and it should tell you exactly what is there, and what could be there. Another thing, it is possible to add these afterwards, and many times the wiring will be there. For instance, I added the factory foglight switch and relay, but the pigtail and wiring to the the front drivers side where the front light harness connects was already in place. I just had to add the switch, and the relay on the other end and it was good to go. Another example of this is putting in my overhead. My Pioneer didn't come with one, but I found hidden up under the dash the connector for it that would connect to the harness running from the kick panel upinto the headliner.