Snake on a Train

It's a snake on a train.  Now, it's a big cleaning bill for that snake on a train. A woman in Boston lost her 3 foot pet boa Penelope on a train and couldn't find it.  Later it was found and now the woman is being sued for clean-up after the snake.  She is just happy to have her pet back.  I want to know why someone is allowed to have a snake on a train, and how no one notices it disappearing and then no one can find it.