I was 15-16 years old on a train to the airport, to go visit my home country(I don't live there anymore). I was probably kind of nervous about the trip, and I probably checked my ticket to see which cart my seats were in at least ten times while waiting for the train. When I get inside, I find my seat without issue and sit down.

I ended up chatting a little bit with some dude in his late 20's/early 30's who was sitting right next to me. When the ticket guy comes along to check my ticket, I dive into all my pockets looking for it. I had way too much shit on me, like phone, headphones, probably an MP3 player, some snacks, etc. The only thing I could find was the ticket for my seat, which is printed separately.

The ticket guy asks me to step out into the hallway with him, and he ends up believing me, but wants me to pay a fine which was much more than I had or could afford. A couple of minutes in, the guy I was sitting next to comes out into the hallway and tells us that I can just ride using his extra ticket.

Turns out he was going to fetch his brother at the airport, and there had been some kind of offer on a fair for two people back and forth. So he was riding down to pick him up with two tickets, one of which went unused on the way down there.

It was really random and pretty much saved my day. I'm not sure what would have happened otherwise, other than me being told to get off at the next stop and then missing my flight, which would've been a major catastrophe, since my family was broke as fuck.