I'm with you ...never enough pockets!!! I use that little one for a spare set of keys. Lock my self out of the car once and never again!
I keep a spare car key in my Tokidoki makeup pouch (I always carry one... and there is a small carabiner in there that I attach my key to.) I have also locked myself out of my car ONCE and never again! (and that's exactly how I put it too.)