Check that horn, indicators and low/hibeams work.
Also check that when on hibeams, the lowbeams are also lit, one of the relays does that and on LHD version it under the steeringwheel.
If everything works... well its Luigi missing an extra relay
I think it will be either the Rear window heater relay or the Horn Relay, It could also be an ignition switch discharge relay but i think you would have noticed that
Just under the steering wheel where the drivers right knee would be is an access pannel for fuses.
This diagram shows the front of that fuse box.
But hidden away on the back of that black main fuse box are some relays and connector blocks shown here. This is where i think your relay has fallen from. You should be able to see the relays just by looking up from the drivers foot well.