At around two minutes, the late Abe Vigoda as Detective Sergeant Fish answers his phone even though it doesn't ring.
The incident in question occurs at 3:44 with Fish holding his prunes and picking up the receiver with his left hand. There is no ring at this moment because it had occurred at the 3:38 mark, ringing very loudly while Fish was off-camera. During Barney's instructions to Wentworth to go back and interview the theater and buy the coffee cream.
When Wojo is pacing back and forth in the hotel room, his shadow is visible on the scenery representing the sky line outside the hotel.
Throughout the series, there are quite a few scenes where the boom mic is visible. This episode in particular is unique with the mic so close to Wojceihowicz in the hotel room that not only can you see the mic's shadow across his face, you can also make out the shadow of the wind screen on his sports coat.