It indeed is bo3 if you used aerial with sudden death, Fruti.
That scheme was intended to be played as bo3 when it's made.
And as I see, you used that one.
Although, you should reacted before 2nd game started, Nico. Cause it's easy to determine if host made it bo1 or bo3.
First you can see it in lobby and if you missed it there, you'll know after 1st game ends. Bo1 sends you in lobby, bo3 would keep you to play 2nd round and switch player that starts first. But I'm sure you know all of this.