Galio Ult Bug [Gameplay]

I was playing Galio the other day, and I ulted a Katarina. She then proceeded to walk right out of it; no taunt or anything. She had no rebuff items, and when I asked, the summoner said they didn't know what happened either. Not sure if it was a glitch or if there's a bug that needs fixing, but just thought I'd say something.

I was standing in the Red jungle at the intersection between blue buff and the wolf camp. A little closer to wolves, and me and one other champion were chasing a low Kat. She was close to the top-most wall when I ulted, and she then proceeded to walk past the wolves after killing my ally. I think my ally was a Vi, but I don't recall.