This is why I always carry a knife when I'm out alone. It doesn't require a permit (that I know of), just don't wave it around and cause trouble.
If I were you, I would have pretended to have a weapon in my back pocket and reached for it like I was about to pull it out. That'd probably never work though. :D
By the way, you should use the iPod tracker app if you have it. Those are really useful.