I did write in, and note I managed to use the forward bathroom once, flight crew all the time and a few other passengers... here is extract of response I goto back:
After review of your email with our maintenance leadership team, I was informed the forward business class lavatory was inoperable due to a broken drain. I am sorry our flight crew did not make a announcement to provide explanation as to why the lavatory was not permitted to be used.
Flight operations, maintenance and the flight crew elected to operate the flight using the two lavatories in business class versus canceling the flight for today. We try to anticipate any issues on the aircraft before it goes into service for the day, and regret this was unable to be fixed before the departure of your flight. I apologize for failing to meet your expectations.