It's fiction. If there can be cellphone induced zombies, then there can be colt .45 revolvers with safeties on them.
I've seen this excuse used before, and I don't buy it. It is the author's job to create the world. He can create what he wants, but it is also his job to inform the readers of the rules of his world. If he wants it to be the real world +/- a few key details, well then he needs to get his real world facts right.
Otherwise you run into too many scenarios where any author can just invent magic to get his hero out of any scene. You want zombies cause by cellphones? sure. However, you have the hero outrun the motorcycle the biker thugs are casing him with because he was a highschool track star? Well, at least you better introduce that superpower beforehand, or allow the hero to be astounded by his own feat, or something. Even within his own created world, the author must be consistant. The audience/reader will never be able to be in suspension if the author is constantly deviating from the real world because the audience will never know when the character is really screwed or when some fictional power or device will allow him to easily escape.
Science fiction frequently has this problem, it is one of the reasons sci-fi never really gets as gritty or as horror filled. Look at all the times in Star Trek when there is some problem beaming people from place to place. Then some guy mumbles some stuff and wiggles some things around and poof, back to normal.
Even in a world with zombies, I expect a person burried alive to run out of air and die. Sure, in a world with cell phone created zombies, the author is in his rights to do anyhting he wants, but it is my real world understanding of the limited time a person can survive in a tiny closed space that gives the scene it's drama. If the person is able to live indefinately without oxygen, that sucks any dramatic potential out of the scene. If you don't know when the author is going to throw in a silly new rule, ALL dramatic scenes lose their potency