Mark of the Kindred in Howling Abyss Bug

About 48 hours before patch 5.18 was announced in North America - I was playing ARAM in the Howling Abyss. After the game started, I bought my items and walked down to lane. As I did this, a blue circle formed around my character very briefly, and then a swirling icon appeared over my character; only to disappear into nothing after a second or so passed. It was strange. I had seen champions use their "Champion Mastery" icon during taunt, and just wondered if there was something like that happening. I paid little mind to it. "It was probably someone's skin." I thought. "Probably making an icon appear over enemies or something."

When Kindred, The Eternal Huntress was revealed - naturally, I checked everything out. Her passive, Mark of the Kindred, is exactly what I saw during my ARAM match.

I understand that bits and pieces of later patchwork are woven into updates prior to release to make launching updates easier for everyone. I just wanted Riot to be made aware of this happening just in case it becomes viable knowledge later.

It's sad that I have no screenshot or recording of this - It was over before I even realized what was happening.

Has anyone else encountered this asset bug in game?