The songwriter is standing at the secretary's desk, holding a briefcase and sheet music. After he walks away with them, the camera cuts back to her but the briefcase and sheet music are still in the shot.
When Rob starts mouthing the words to the song "Bupkis" on the radio, it looks like he mouths "diamond ring" but the song says "diamond mine".
Rob dials the number of radio station WIFE, before he looks it up in the phone book next to the telephone. He says, "Right" as if to confirm he knew the number, then chuckles in spite of himself.
When Rob hears the song "Bupkis," he calls the radio station. He first dials the number and THEN looks it up in the telephone directory, saying "Right." Dick Van Dyke's grin and body language plus the audible laughter from the crew reveal that Van Dyke was covering for his mistake.