Yeah, the “uncle” is way off.
Here’s the plan:
1. Use the web to determine the flight number of a regular flight from your airport to Baltimore.
2. Check arrival gate for that flight on the airport website.
3. Hop fence, go to that gate.
What probably happened is he got disoriented and went to the wrong gate, or they switched gates, which happens occasionally. Then he ended up on a Boston flight instead of a Baltimore flight.
That's probably exactly what happened. I think some folks don't realize just how resourceful a sixteen year old can be when he wants to do something that he isn't supposed to do, and thinks he can get away with it.