Steve took the non-verbal to mean: maybe later, probably never.  He made a mental note to ask Sam for suggestions to encourage Bucky to start getting a bit more out there.  He knows he's probably spoiled himself with Bucky's undivided attention so far. 

"Excuses." He whispered against Bucky's lips before closing his eyes and losing himself into heat and pleasure of the kiss. He suspected this wouldn't be the last kiss they'll be indulging today but he couldn't think of any better way to pass the rest of the day.