Untargetable Ezreal?

About two days ago I was playing . I provided a gank to mid, being my target. I used my ult, leaped, then q'd but for some reason my q never went off (This was as he was casting his ult). I didn't even attack him - it was like he became untagetable. I sat there for a solid 2 seconds trying to figure out wtf happened.

Can anyone verify or check it out?