Most people seem to get caught out by dumb shit like text messages on phones they leave around for their partners to see.
I'll lay out an example for you: I'll play the wife, and let's say the DH thinks I'm boring and unsexual, so how would he ever suspect? He doesn't bat an eyelid at anything I do, wear, say, doesn't ask me where I've been, or who with, or why I'm home late. He literally cannot conceive of an affair because it probably doesn't occur to him that a) I like sex, or men and b) no one would want me. He's never checked my phone, doesn't follow me on Facebook and has literally, genuinely, no interest whatsoever in any aspect of my existence. He appears incapable of suspecting.
I don't see why the article should be considered fake just because the Mumsnet consensus is that all affairs are caught out. No, just the clumsy ones who leave their phones around.