Ziggs Q not damaging Yasuo

Played a game of aram, not only were Ziggs Q's going through the character model, ok i might have missed. But I noticed on several occasions that my q would hit Yasuo, but he'd not take any damage whatsoever. Now I know he gets a shield and it could be poorly timed hit with his flow passive, but when it happens more than once it doens't seem like just coincidence. I might add that those two times, i wasn't dreaming, he didn't use windwall. He was playing the the mechanized Yasuo, and its hard to miss that orange shield on a white and blue map.