Receiving the next wave of F2P champs before they are released

[Client?] - I noticed last night that I was able to play champions I do not own and that were not on the current champion rotation. I figured out that they were the next wave of champs when I saw a notification on my phone from an app that tells me the F2P champs. Along with being able to play more champs than usual I also lost some, but not all, of the current rotation, specifically: Thresh, Janna, Maokai, Udyr. Kind of a weird bug and I have never experienced it before.