They didn’t know until after the game. It also just keeps proving that just because someone has it doesn’t really mean much (unless you’re elderly or have some type of underlying condition)...as they all played in the game (or could have) and had no symptoms whatsoever.
Also, knowing that the testing and results themselves have been pretty scatter shot and not reliable, what are the chances they don’t really have it anyway?
half of a baseball doesn’t test positive by accident.