That is a ridiculous amount of time to wait, especially considering that there were 3 employees present. Unless there was an urgent/emergency matter, the responsible employee should have acknowledged you right away if they could not help you immediately, and then they should have gotten your cappuccino very soon after. If they could not help you, and their 2 coworkers could not help you, they should have requested back-up from a manager. (I sure hope one of those 3 employees was NOT a manager!) A customer in your presence always takes precedence over other tasks. After all that, I also hope your cappuccino was comped. That would have been the least they could do for you after your 20 minute wait!