It takes a minute or two for Steve to make that eye contact. He's just as disoriented as everyone else on the platform, and his new (ten-year) habit is to look from right to left now, automatically checking people around him for injuries.
And when he does manage to look over his other shoulder and sees Bucky, his first irrational emotion is relief. Because, even here, his friend has followed. At least until he bolts. It's all too easy to fall into the chase, mostly because he has no idea why the other man is just taking off, but also because WHAT IF HE'S INJURED? What if something happened between the battle and landing here that he didn't see. He can't be responsible for Bucky getting wounded again. He can't. Hence the speed he's now exerting to catch up.
on your left
And when he does manage to look over his other shoulder and sees Bucky, his first irrational emotion is relief. Because, even here, his friend has followed. At least until he bolts. It's all too easy to fall into the chase, mostly because he has no idea why the other man is just taking off, but also because WHAT IF HE'S INJURED? What if something happened between the battle and landing here that he didn't see. He can't be responsible for Bucky getting wounded again. He can't. Hence the speed he's now exerting to catch up.
"Hey, Buck! Wait!"