Originally Posted by
amoreira
IMO as a train conductor it is your responsibility to check everything and ensure that all is in order. You already left feedback, which leaves people with the impression that you accepted everything on the train as it was, so I think that changing feedback would be wrong. It is was the train passenger's duty to send an unused stamp, but it was equally your duty to check and ensure that all boarding passes were there and correct. This is a time to let bygones be bygones and just make a mental note to not let that person ride your trains in the future.
Just my 2 cents.