Possible bug (or hax): Sion used Flash while in Passive form

Title says it all. Unfortunately, while I do have it recorded, the league replays keeps on bugsplatting. Nonetheless, I would like to report this issue where me as Singed, low hp, flinged away Sion who was in his Passive form. He then flashed somehow and killed me with a last punch. My friends who were on skype with me yelled ''WTF'' because as far as we knew, Sion is not supposed to be able to use summoner spells when his passive activates. If my replay works somehow, I'll post a video, but srsly, how could that happen, it left me speechless.

https://www.youtube.com/watch?v=gzsp3GmrHmg&feature=youtu.be

If there is more I should have added to the video, please say so.