I've only been punched on the subway.

I was underground the only time I've been punched during a transportation dispute.
(The only time I've ever been punched in any dispute, actually.)
I refused a swipe on some young thug’s card, so he punched me.
I, only a little flustered, took out my Metrocard and got on the train.

These guys (http://www.nydailynews.com/news/crime_file/story/334719p-285998c.html) had a similar predicament.
Only they stabbed the puncher in return.

I don’t carry a knife.

Also, my situation seemed so absurd that I couldn't help but laugh.