You had been forced to stay behind after class was finished for a lecture. While Gojo-sensei was finishing up some papers, you look across the classroom to the windows connecting to the hallway and see your friends jumping up to them (as the windows are super high).

They wave each time they jump up, make heart shapes with their fingers and point at you, generally just trying to make you feel better. Yuji even lifted up Nobara a few times so she could see you better.