Your dumb.
I am a pretty big guy and can throw, but in a situation like that...where there is a good chance dude probably was on drugs, the kid did the right thing. All the kid had was a knife.
If the dude had a gun, and he really was fvcked up off 'something', he wouldn't think twice about using it. Leaving a good chance the OP could have been seriously hurt if not dead, and the dude driving would either get away with the crime or end up doing time for something he committed while on drugs. Happens all the time.
True, being on sherm does not stop the ability to be knocked out, but you never know if the guy had a gun on him.