Missing ARAM Loot

So, recently I played a game with Katarina in ARAM and I received an S plus, which gave me a loot chest. Soon afterward I got an S plus on Teemo and on Xayah, however, I did not receive any loot chest. Mind you, this is the first time this season I have gotten an S grade or higher on either of these champions, therefore, I am wondering why I have not received a loot chest. Is anyone else running into an issue like this? Does anyone have an explanation? [sg-janna]