Two of the same champion on the same team (Team Builder Bug)

I join into a builder with another teemo...

We are all confused and the owner of the builder says "i clicked really fast" sadly the teemo left not realizing we had discovered a bug and needed to see its affects in game. This is not fake and all the information i know we went into game with a mid lane yasuo after the other teemo left. I do not know how to reproduce this bug other than to "click fast".

Match URL: http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/1885093759/214190504?tab=overview