Free Ashe Skin (not spam or me giving one away)

So was going through champions I owned and skins I owned. Apparently I own the Frejord Ashe skin which I never bought, not complaining but was like when did I get this skin. Googled to see if Riot gave it away for some reason at any point and apparently it was a glitch for the Riot Girl Tristina skin. Not sure how or why but I received the Skin for free and was curious how true the post I found was.