Yesterday, I took an inter-European commercial flight with a popular budget airline. Before take-off, the captain announced that the First Officer would be taking the entire flight today.
During the middle of the approximately 2 hour cruise, the seat-belt sign came on. The flight attendant, who was next to me at the time, quickly turned to look at the front of the cabin.
The captain came out of the cockpit, a flight attendant took his place and locked the door behind him, he spoke over the PA system and asked everyone to fasten their seat-belts. A couple of people stayed up and he firmly told them, again over the PA, to sit down and fasten their seat belts.
Despite largely overcoming my fear of flying recently, I was slightly alarmed at this point, so I asked the flight attendant if we were expecting some turbulence. He told me that no, we weren't and that the seat-belt was only because the captain needed to use the restroom.
Sure enough the captain used the restroom, came out, re-entered the cockpit and a few minutes later turned the light off.
My question - is this standard procedure or is it likely the flight attendant was giving me the 'passenger friendly' version of the story? I have since wondered if it was the FOs first 'solo' flight and if that might have been related.