[Gameplay] Malphite Unstoppable Force Interrupted by Shaco Box

I was in top lane with Malphite against a Shaco who, surprise, liked to play in the bush with his box (giggity). At lvl 6 I had what I thought was an opportunity to catch him and maybe win the fight, but it did not work out that way at all. I was on the purple side and he was in the bush closest to my tower with 2 or 3 boxes around him. I ulted from the minion ball that was closeish to my tower into the bush. I made it almost all the way to the end of my travel when his boxes feared me and interrupted my ability. I was close enough to him that had it completed he would have been knocked up, but nothing happened, no knock-up, no damage. Just pain and frustration. for me. I'm sure he was ecstatic. We ultimately won the game through teamwork and objective management even though the enemy team had twice as many kills as us, but that bug sill bothered me, because I had always thought the point of Unstoppable Force was that it was, well, unstoppable. I don't know if it was a one time thing or not, but I hope it can be recreated. I don't have a recording of the event.

Thank you for your time.