How the minds work

So I go in and get the exact same coffee at a particular coffee shop usually. Today I wanted a juice. So I ask for the juice, and the barista gets me some coffee (the usually mild brew) and then charges me for the juice. After a few moments, he realizes that he hasn't gotten me the juice, he got me the coffee. The coffee machine is to his right, the juice to his left. He heard me ask for the juice, and it was internalized so he knew what to press to charge me after he made the coffee. Now, I was going to ask why he was making me coffee, but there were other people waiting for stuff and the person making the sandwiches, etc., looked overwhelmed. So I had thought that he was getting coffee for someone else before snagging my juice out of the cooler.