[GAMEPLAY] Vi ult stopped by Poppy W!?!

In a late game team fight, I hit my ult (as Vi) onto Vayne who was on the other side of the enemy team. In other words, I was ulting Vayne through their team; the Godlike Vi setup. Poppy (on the enemy team) had their W up, and even though my ult animation started (red targeting line going to Vayne etc.) my character got suspended mid-animation for a second, and then just stopped. I know poppy W is not supposed to stop Vi ult, and as a late game team fight, this most likely costed the ranked game. (They ended immediately after.)