I'm using a Samsung Galaxy A10E, OS version 9.0. 

The champion was Juliana, she's an Epic tier Sacred Order Attack based champion; I had her at level 40 with only 1 ascension star and mediocre crit rate artifacts equipped. 

Before I noticed she was gone, I was ascending and leveling champs through the tavern as I normally do. She has been locked since I got her- all epic tier champions start out locked from the moment they are summoned anyway and I know there's no way I unlocked her or used her as fodder for another champ. 

This is very frustrating because I had gotten her from my first Sacred Shard and she boosted my CB damage quite dramatically and I've been grinding really hard trying to get better artifacts for her. 

I never thought to take any screenshots of her because this has never happened before so I didn't think the game could possibly eat one of my champs. I've tried reloading the game multiple times to no avail. Please help and thank you for your time!