When Tony saw that the Conductor announced that Peter was on the bus, he felt some mixed emotions. On one hand, Peter should be at home enjoying the life that he just got back, or maybe for him, he'd been back at it for a while. He knew that the bus could bring people from any point in time. Being on a bus that travels dimensions was admittedly insanely interesting, but Peter should be home enjoying some sense of normalcy (as much as a superpowered teenager could get, anyway).
And yet, Tony was elated at the idea of getting to actually see him. While Bruce had brought everyone back, Tony had come to the bus before they had gotten to see everyone again. He'd heard about the big epic battle with everyone there, but hearing and seeing were two very different things.
Instead of sending him a message (felt too impersonal), he left his rooms, searching the bus for him. The place was bigger than you'd think a bus should be, so it took a little bit to find him. Knowing Peter, he was probably exploring the thing, too, so he was probably just missing him in different places. Finally, he spotted the kid down a hallway. Hopefully, the kid didn't think he was a ghost or something.