Cassiopea W is invisible

Well the whole game long enemy Cassiopea when casting W it wasnt visible the area on the ground. It was not visible from my entire team ..enemy team didnt show any indications whether they see it or not. That's all info I got.

Team comps - Shaco,wu,ziggs,vayne,shen
vs cassiopea,yasuo,trundle,gankplank,kassadin