I asked Misha prior to the prophet's arrival at the devotional if she had ever been in the same room with a prophet before. She said that no, she hadn't. I explained that when he walked in to the Marriott Center there would be an instant hush of the crowd and that the students would stand quietly until the prophet was seated or had signaled to the crowd to be seated. I remember it being a pretty powerful experience for me when it happened at Ricks College.
After the devotional, President Nelson rose and began to wave to each section of students; they, in turn, waved back.