Getting coffee in a line can be awkward. Often times the barista assumes the two orders are together. Not having been there, it’s hard to know for sure. But if they said “anything else?” and you looked at him, that was you agreeing to pay.
I find it’s best, before any date, to say that you only go Dutch treat. (Everyone funds their own way). The expectations are set. No one owes anyone back, and no one can feel like they wasted money if it doesn’t work out.
Later on in the relationship, I personally find that splitting based on financial position is the best way to keep things equal. If I make twice what they do, a fancy restaurant that I suggest might be financially insensitive. If it’s a 75/25 split, that’s more fair to them.