He didn't know how to do this. How did he explain everything that had happened to his friend? There was so much he didn't know. This wasn't Bucky missing a few years. This was everything. The fact that he was asking about the presence of his arm barely even registered.
"I was on Schmidt's plane. The Valkyrie." As though the name had any relevance right now. "But there were bombs onboard, and it was heading for New York. I had to take it down." Too many innocent lives would have been lost if he hadn't. "They found me in the ice seventy years later. The serum kept me alive." That was the most simple way he had of explaining it right now, not knowing how Bucky might react. This was different. This Bucky hadn't been through everything he had over those years.
"You, well. You survived the fall. Those experiments of Zola's. You ended up with Hydra. Got a new arm for the trouble." He tried to be a bit flippant and failed spectacularly. All this was doing was dredging up memories and guilt he spent enough time willfully ignoring. "If I'd known, Buck..." He had to know he'd have come for him.