How you ask? Simple. Reading comprehension. Just how you read the threads to pick up the coupon, you should continue to read the threads to find out it was a old expired coupon from 2011, that should not be working especially for rentals of just one day. It was posted the same day. Let's go back 15 years and find me any other MONEY OFF coupon with such a high value for any rental of short durations. That's where moral ethics and common sense kicks in. Great if you can get away with it, but don't expect it as a given. Alamo owe's you nothing (nor does any other company if it happens). Bad IT is not a valid complaint for D.O.T to do anything, nor enforceable.
Anyone who rent's cars with frequency knows Alamo website is glitchy on it's best day. Thus I would NOT expect a retired coupon that dates to 2011 and suddenly became active again after website maintenance, to work or stay on a reservation. My guess is they aren't even aware the coupon is active again yet, but the system is properly kicking it off at the departure booth. With that said, everyone on this board should know there is no coupon EVER that works for $50 off one day rentals. Can't be inhaling the pixie dust that much. You follow and monitor these threads and it's never happened so a obvious glitch.
Walking into Target is apples and oranges. Target prices their items themselves. Manually. Of course if the sign says one price they are required to honor it. Not true in cyberspace. Two examples. When Walmart accidentally filed something as 99 cents instead of 99 dollars online about a year and a half ago, they promptly issued a apology and canceled every single order and refunded everyone. When United filed a mistake first class fare in Swedish currency that made first class tickets to the US only hundreds of dollars a year ago, they canceled all the mistake tickets and apologized. The Department of Transportation sided with United and said they did not have to honor an obvious mistake. IT mistakes/glitches does not require the company to honor anything.
Enjoy your trip and the Magical Express.