The reason that Ronda Rousey did not appear on tonight's episode of RAW is because she was away filming something for Shark Week on Discovery. Below is WWE's announcement:
Ronda Rousey will not appear on Monday Night Raw tonight, as she is currently filming for Shark Week, which begins Sunday, July 22 on Discovery.
Although Rousey is typically sinking her teeth into the Women's division on the red brand, this week she is on location for an as-yet unrevealed piece of Shark Week programming.
Rousey will likely return next week to continue the storyline with Natalya.