I just had a game on Live Server, the enemy Ornn player said that the game doesn't show his element on his screen so he can't redirect the element to my team and knocked us up. I saw him summoning thrice in that game but he didn't react at all. We had a Braum in-game, but he didn't block his summoning so it could be a visual bug.
We tried to reproduce the bug in a custom game but it appeared fine on my side when I used Ornn.
I will list the champions used in that ARAM game for reference. I do not know exactly how it was triggered so I hope the list might narrow it down.
Braum, Rakah, Ezreal, Morgana, Gnar
Cait, Nami, Irelia, Malphite, Ornn