I have given up with leaving my car keys with the rest of my kit. Even if I am leaving my kit in a locked building, I now follow these basic steps:
- (if you leaving your stuff in a changing room) When you are getting changed and ready for the game, do not put your stuff back in your bag when you are leaving it to go ref. Leave it outside the bag! If someone is going to nick your stuff they will be less likely to put all your worthless (to them) bits and bobs back into the bag before taking it. They are looking for easy to nick valuable items like wallet/rings/keys/phone which you will have hidden elsewhere anyway (car etc) and a nice, neatly filled bag will just be picked up and walked off with.
- Get an arm wallet. The most valuable item with you will be your car. Lock your phone and anything of value out of sight in the car. Carry sandwich bags or similar and put the key in there and then in the arm wallet. Even if the heavens open and it pees it down, the key will be dry and safe!