We discussed the "spare key in the seat bag" and decided that was like putting the door key under the mat. It would work...only if you remembered to remove the spare key from the seat bag every time you locked it up. My husband would very likely remember to take it out, but forget to put it back, leaving himself in exactly the same situation next ride.

Another funny quirk to this story is that a couple weeks ago I had to rescue him on my bike when he locked his car key in the car.

I'm starting to see a pattern.