Happened to me as well. I opened a ticket and they just told me I did receive the reward. Placed 4th and silver kane was the reward but he remains locked in my roster so they're full of crap. Ticket was no help. Just got screwed. And yes I clicked the reward button right after I clicked the one for lub reward.
Opening a ticket didn't help. They just told me I already received the rewards. Silver kane was the reward yet is not unlocked in my roster but I guess it is what it is.