What is "Loss Of Ban"?

They did something wrong, likely having something to do with Big and Keith not being there, that led to them not being able to ban any champions for the game.

Kinda wish I knew what was going on. Kieth and Big played yesterday. did they get lost in Bard's Magical journey or something?

Most likely didn't submit a roster in time

It's usually due to the starting roster not being locked in in time. Happened to C9 last split when Hai came back.