You've all defined the problem. I agree. I'm not sure a laminated card in the glove box would be enough ("Reminder: Safety Kit & Clothing with Spare Tire").

Based on actual disasters we've seen, is there a point at which ordinary people start digging around in the corners of their vehicle? Maybe Day 3? Or does it never occur to them at all? Even in an otherwise naked rental car, I would have the tire iron out at least.