There are only 4 teams in the tournament, so if you're right that Gonzaga beats SMC and BYU beats SMC, then they would play the loser of the LMU vs Gonzaga game. Or, if it's the other way around and SMC beats Gonzaga, then BYU would (assuming they beat Gonzaga) they would play the loser of LMU vs SMC.
So, "someone else" could only be LMU.