No. I don't think it was Yogscast who found it, but someone on reddit. After that, these fame-hungry bastards made a video of it and everyone thought they found it.
Ooh, bashing on the Yogscast for no reason whatsoever; aren't you the big and clever one.
I've almost certainly had the Minceraft logo show up. It's a 1 in 10,000 chance and I must have booted up Minecraft close to 10,000 times. I've just never noticed because I don't look at the title any more. I don't even look at the splash text any more now I think about it.
If it's a 1 in 10,000 chance, and if Minecraft has been out for 3 years (that's quite a generous number) you'd have had to boot up Minecraft almost 11 times a day in order to have likely seen it by now.
I'm it's overlooked more often than not. Notch probably meant to keep us off balance thinking it was a hidden feature (aka, "removed herobrine.")