i was botlane with corki and enemy team was cait/ imperial lux skin, lux's e wasnt appering when she cast it or when it was sitting there, helpd us lose lane being unable to tell where the e was or when she cast'd it. i belive the bug was created when the lux chose the skin, i also have suspisions of the lux player intentialiy using the bug
Ive seen it happen with lux's that werent using a skin. Its been happening on and off for like 3 weeks now. You think its scary with Lux's projectiles going invisible... wait until you see it happen on Nidalee spears. 
seems to be a common skill shot bug. Have had this happen with morganas and ezreals as well. You can see the spell but its only the outline. no effects or color fill. Easy to sharpen your eyes and see the outline of morg's but, lux and nida's not so much since the missiles are much smaller.
