No it was not.
https://support.riotgames.com/hc/en-us/articles/201752944-Guide-to-Legacy-and-Limited-Skins
Championship Riven (given away during the Season 2 World Finals and 2014 World Finals, no longer available)
The 2012 version of that skin was not available in any way outside of getting it either in 2012 or when they had given it away for people that won the Wolrds Pick Em challenge in 2014/2015.
It is just like how Pax skins, Urf Warwick and several others are NOT part of Hextech crafting.
http://na.leagueoflegends.com/en/news/community/q/urfwick-wants-loot-box-and-voice-chat-and-better-support
Giveaway only skins include things like PAX skins. They’ve only been distributed through giveaways. Previously sold skins are limited and have been sold in the store and include Urfwick, Championship Riven, Riot Squad Singed, and Rusty Blitzcrank. For giveaway only and previously sold skins, such as Urfwick, it’s possible that some version of those skins could return via Hextech Crafting or some other means
Until we have a plan that follows both our rarity and Limited skins philosophies, you won’t be seeing skins like Urfwick in Hextech Crafting
It's just like when they had the E-sports gifting in the store in the past and I owned every E-sports skins BUT Championship Riven, where I asked a friend to try gifting using the E-sports option and it wouldn't let them cause it said there was no content available.
So there was no possible way to get it before 2016 in the store or chests.