Stuck into the wall by a creep

This just happened in my last game and is the first time i have seen this. I am well aware of "creep block" and how you can not travel through a minion and if they clumped you can not progress forward and have to progress backward in some cases. This is not one of those cases. I was top lane rumble fighting a sion i just finished killing him and was running back when a creep got in my way no big deal. However, it stuck me up against the wall and the creep bugged also and would not progress i was caught on wall for atleast 5+ seconds while dead passive sion wailed on me securing a free kill.