Steve waited for Tony to call him.
It's not like he was just waiting by the phone, pushing everything else aside as he waited for Tony to call him and ask for help. He wasn't ignoring his responsibilities in favor of answering the inevitable call.
Still, that phone was one of his top priorities. It was always in his pocket, no matter where he went. It sat on his bedside at night. It rested on the counter when he showered. It didn't matter where he was, what he was doing, or who he was with; he had the cell phone on hand so if, no, when Tony called him, Steve would be ready for him.
A large part of him had hoped that Tony would call soon after he sent the phone. Like Steve had said in the letter, he had a lot of faith in people. He found good in individuals, even when he shouldn't. It was one of his best qualities, but it did more harm than good as time passed. He kept waiting, sure that Tony would call any day, any hour, any minute. They were a team. All teams had arguments, but they needed each other. This conflict would blow over, and Steve could go to the closest thing to a home he had had in years.
In the meantime, he watched. He interfered when he thought it was necessary, but flew under the radar. That had always been easier for him than it was for Tony.
He kept an eye on the boy from Queens. He had a soft spot for the kid, and he knew that Tony would make sure he was okay. Tony may not have been able to save himself, but he could protect another good kid without a consistent father figure.
He gladly watched Tony's wedding to Pepper, proud that his friend had patched things up with the only woman who could ever have handled him.
He watched, with mild horror, as Tony moved the Avengers headquarters. Sure, he had said that it was Tony's team more than his own, but he hadn't expected for Tony to change it so much.
He hadn't expected Tony to ignore him.
Steve stood outside the new Avengers headquarters, flanked by Bucky, Sam, and the other heroes that had sided with him when the rift began. Natasha had called him when it became clear that the war with Thanos was nigh. She asked him to come, so he did. He ignored the sinking feeling inside when they hung up, knowing that Tony must not want him there if Tony hadn't called. Steve couldn't quite wrap his mind around why Tony refused to get the team back together. They were at their worst when they were alone, Steve especially. Steve had always flourished when he fought alongside his friends. Friends brought out the best in each other, both in fun and in battle.
Why would Tony refuse to fight with the team when it was clear he would lose when he was alone?
Steve walked in the front door with more confidence than he felt. Tony stood across the room, waiting against the wall.
Tony looked older. His wrinkles were set deeper into his face. His eyes were tired. It had only been 2 years since they had last spoken, but Tony looked different. He looked broken, Steve realized. The good humor was gone.
"Everybody else is in the back, waiting to make a plan," Tony said crisply. He looked over the new group quickly. "I hope you have more tricks up your sleeve than last time we met. Thanos won't go as easy on you as we did."
Normally, Steve would have had a response to this. He would have made a joke, or rolled his eyes, or something. He would have met Tony head on. Now, he wasn't even looking at his old friend. His eyes were caught on something else.
Looking around the room, Steve saw the clutter of old friends. Papers of all kinds were scattered across the room; blueprints, notes, and newspaper articles. He could see Natasha's favorite books and magazines, which Steve knew she only left out when she wasn't worried about who could see them. He saw clothes that must belong to Vision, who was terrible at putting his belongings away since there were no boundaries to hold him. A backpack and clothes made for a teenager were tossed haphazardly in a corner.
Tony tracked his gaze. Steve looked at Tony's face for a split second, managing to catch and identify the various emotions before they faded. Tony looked at his friends' things fondly. The most love was on his face when he saw Peter's things. There was a soft look, but it faded to a cool indifference when he looked back at Steve. "If I had known I was having guests," he said levelly, "I might have had Dum-E clean up." He didn't wait for a response, opting instead to leave the room for what Steve assumed to be the conference room.
Steve followed dumbly, ignoring the questioning looks from Bucky and Sam. He finally understood why Tony had never called him.
Tony had not needed him. While Steve was away, he had built himself a family. Tony had gotten married. He had trained and bonded with a really good kid, one who seemed as fond of him as Tony clearly was of Peter. Tony had built a home for a ragtag group of misfits, and he never called Steve because he hadn't wanted or needed Steve to be a part of it.
Tony may need them to help defeat Thanos, but he had waited until Nat called Steve to prove an important point: Tony only needed help with Thanos. He did not need to get the team back together. There would be no revels if they won. This was not a reunion. This was business.
The home Steve had longed for had changed when he left, and there was not a space for him in what the Avengers had become.
Tony had moved on, and Steve needed to do the same.