You forgot to mention that the only solution is to wear the sweater as pants. So he squeezes his legs into the arms of the sweater and pulls the rest of the fabric tight around his waist. He can only keep himself covered by hunching over. Walking will be a new challenge altogether. Rather than going through the absolute trauma of returning to his seat and explaining (or creating an elaborate lie to explain) the entire incident, our hero waits in the bathroom until the train stops at the next station. He waits until the moment the train starts to pull away from the station, then dashes out of the bathroom (as quickly as a hunched over cowboy with sweater pants can dash) and jumps off the train. He is lost and stranded somewhere between New York City and Westchester.
He hasn't seen the girl since.
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Save Chip - Don't let Sarah win!
Official Titterer of the Laughing Hyenas