The face he saw was not one he recognized. Bucky had been hoping for it to be Steve or one of their allies, perhaps someone from Wakanda he'd know who might be able to explain what the hell had happened, but he was instead met with a woman he did not know. She looked young. Not juvenile, but younger than him for sure. And while she presented a reaction to him aiming a gun she didn't seem particularly afraid of it either which he found very curious.
Bucky did lower the gun but he didn't put it away just yet. It wouldn't be a stretch to say he wasn't exactly trusting. Nothing against the young woman who'd shown up, but given the way the world tended to work Bucky was better off not opening up to everyone he met. He didn't want to give off the impression of vulnerability by admitting he was lost, but he really did need answers so he had to sort of go there despite his instincts fighting the logic in his head.