It looks like someone at AMD messed up and accidentally revealed the new Vega logo one week early. Several tech sites like Legit Reviews noticed it and took a picture of it. The logo was shown during the presentation but at the end of the event the same slide was shown without the Vega logo.
It looks like someone put the unannounced Radeon VEGA GPU logo in the slide deck for the Ryzen presentation. The Radeon VEGA logo was never spotted again, but the cat was already out of the bag and hundreds of journalists were shown the logo for VEGA.