Vayne tumble or feature

I was playing against . Jinx has Flame Chompers, snare grenades, thought that'll be a good CC against her tumble.

I used those grenades so many times yet vayne would tumble thru them yet not get snared. Usually her tumble makes her visible, i was able to see her becuz of pink wards & once she did it under my tower.

If you think it is not a bug please explain on how to CC or stop her tumble? Is her tumble supposed to dodge CC ? I thought it is supposed to make her invisible not untargetable. Or is it that grenades only work if enemy is visible ?