More than likely legit. As for how they found it, hidden images like that sort of sound like bursts of modem noise, so if there seem to be repeating patterns of something that sounds like what lifting the phone up when you were connected to the internet or a BBS over dialup, it's a good...
Not surprised. It's a Wired article. One day they used to be credible, but nowadays, well, if it's not Apple or some hipster bike product, it's garbage.