Humour me…in your boot…on one of the sides where there is normally a kit of some kind, towing eye that sort of thing. Under that should be another compartment. Look in there. Believe it or not, my dad’s M3 locking key was missing when he took it to be detailed. Main dealer had no clue. BMW recovery was on there way. Some research on forums a 3 series owner suggested looking as above. It was there…