You may only purchase 1 Desert Bus pass. It will only be for sale if you haven't unlocked the Desert Beach by making a bitchin' meatcar.
If you try to buy a negative amount of something:
That isn't a reasonable number in this context. Thanks for trying, though.
If you try to buy something without selecting it:
Remember that time when you tried to buy something without actually specifying what you wanted to buy? That was awesome.
If you try to access a store that doesn't exist, you get an an empty version of this store with the following as store text:
Hey. I'm the Market Demon. You've been sent back here by some kind of bug. You might as well buy some stuff while you're here, though.
References
The Market Demon is a reference to a computer daemon -— a program consistently running on a computer that serves a specific function (like a mail daemon). In this case, he is always online selling things.
The text seen when you attempt to purchase an item without selecting anything is a reference to "The Chris Farley Show", an old Saturday Night Live sketch in which Chris Farley would ask various celebrities if they remembered certain scenes from movies they were in, and then say "That was awesome."
History
On May 1, 2012, The Market Demon was ousted by General Store.
On October 7, 2008, The Market began to sell glittery mascara, completing the trio of +15% stat boost items.
On June 25, 2007, with the advent of NS13, The Market began to sell Ben-Gal™ Balm.
On September 26th, 2006, The Market began to sell the fortune cookie, previously available from the hermit.
On June 1st, 2006, The Market began to sell beer cartilage.