As I ran out to the tennis court a few moments later, I had to pass the open boudoir window, and was unable to help overhearing the following scrap of dialogue. 
I heard some of the dialogue because I have to pass the boudoir window to leave the tennis court.
mnli hypothesis: I heard some of the dialogue because I have to pass the boudoir window to leave the tennis court. premise: As I ran out to the tennis court a few moments later, I had to pass the open boudoir window, and was unable to help overhearing the following scrap of dialogue. 