Bus trip!

My sister invited me to go on a trip with her family. It was to be a bus trip. I accepted. She made the reservations and paid for the trip in one sum. I then wrote her a check (which she cashed immediately) to pay for my share. The tickets were e-tickets and were all on one receipt. We were to meet at the departure point where we were to board together.

Problem?

Her family was late and missed the bus! I had no way to get on the bus! I asked her for my money and she got pissed. We are not talking $20 here. We are talking about a couple hundred $.

My mom says I should keep the peace and just eat the money, but I don't think that is fair. What do y'all think?