Apparently you used to be able to trigger the central locking by kicking a certain part of the bumper - it was a safety measure so if your doors are locked and you crash, your doors unlock.
Or you could push the car round to Vienna Street in Anfield - last time I parked my car there some scally's managed to get into my boot (although it did involve bending the door and smashing a window, so maybe not the preferred option).
My wife did the same thing when I had my focus. We had gone away for a weekend, she took my keys to go into the boot, opened it with the remote key, put keys down in boot, took shoes out of boot, shut boot. DOH! No problem I said, you've got my spare in your handbag. Problem - handbag is in car.
Had to call the AA out - they used a nice little trick of removing the break light from the boot lid and doing some little trickery which I won't detail on here
After that I kept the spare in my trouser pocket, I wasn't likely to leave them in the car.