Other mistake: When Lucy tosses the umbrella off the balcony during the Mexican serenade, Ricky somehow doesn't appear to hear it hitting the floor during the pause and keeps on singing. (00:23:30)
Continuity mistake: At the end of Ricky's song "Lady of Spain" when he sings the verse "all that my eyes are revealing, Lady of Spain", in this wideshot we see Lucy in front of the balcony doors facing forward raising her arms, then in the next side closeup Lucy's still facing forward and a flag has suddenly appeared behind her on the balcony door. (00:21:50)
Chosen answer: It's not known. She may have moved it to the spare room or it may be in a corner just off camera. There could be any number of reasons, though it probably took up too much room on the studio set, and it was removed, making it easier for the actors to move around.
raywest ★