I really don't see what everyone is complaining about! The rules are simple, if you don't have a ticket that covers the day in question the inspector has every right to fine you. It doesn't matter if you bought a ticket every day for the past 20 years, you don't buy a ticket today, YOU CAN'T USE THE TRAIN TODAY! Why is it so hard to understand? Just because you're a regular customer does not mean you get free ride days.
Furthermore, it wasn't a mistake, Spurminator bought an August ticket thinking that by doing so, he wouldn't have to pay the ticket for the 29 of July. That is against the rules. Tickets bought for August only apply for AUGUST! Now, I'm not saying the guy shouldn't have cut you some slack, maybe he should have, but to claim the agent did anything wrong is preposterous. Spurminator has absolutely no legal claim whatsoever.