Hello! I’m from the USA and a native English speaker. :) Did B buy any shoes? Maybe, maybe not. You can absolutely say “I’ve been shopping for shoes” if you went and looked but didn’t buy anything. If you want to make it clear that you did buy something, you could say “I went shopping and bought some shoes.” However, there are some situations where “shop” could imply that you bought something. If you say “I went grocery shopping” it would be understood that you bought groceries. But I think that’s just because people don’t usually “shop around” for food, they just go and buy what they need. I’m sorry if that is confusing! I’d be happy to clarify that more if you’d like. :)