Ashe ult disappearing

Hi There,

I was just in a normal game, playing as Ashe. Every time I used my ult and hit someone, it did nothing - no damage, no stun. There was a Yasuo in the game, but it never got intercepted by a Windwall. It was, however, acting like it did whenever it hit an enemy champion. For example, I was against a Miss Fortune and Leona in the bot lane. Yasuo was in the top lane. I ulted point blank, hitting Miss Fortune, and she just walked away. No damage, no stun. Same when I later hit Leona, and same when I hit Yasuo (he did windwall but it was nowhere near the arrow. We were chasing him and had walked way past the windwall when I fired it off.)

Has this happened to anyone else? I don't know how to get replays, or else I'd post one here.