If this is true, it just confirms that Wyden has no interest in the investigation, just in his time on camera. This is typical for legislators in many hearings, especially the one who cannot think on their feet.
The questions and answers are almost always known in advance (the procedure might be a bit different for someone like Sessions), so once an actor has delivered his lines, he can leave and not miss anything.
If Wyden did leave, it was to clean out his undies.