Submissives with sensitive souls
Submissives are by nature eager to please, so they are especially sensitive to correction from their dominant. Actually, we don't even need to hear them say anything, most of the time. When I see disappointment on my master's face, I just want to crawl in a hole.
You ask if a dom is really upset, or is it part of the play? It depends on the context. If you're doing a school girl scene, and he frowns at you and says, "That skirt is entirely too short, Miss Thing. You need a spanking" -- that's part of the scene.
If he told you to wear no panties, and you're wearing panties, then he is probably upset with a valid reason.
I've known of some doms who will sometimes do things simply to keep their submissive off balance; that's a practice that frankly pisses me off. D/s relationships can't work if they aren't being honest at all times. Transparency is very important.
Some doms use that "play disappointment" as a part of humiliation play and/or emotional sadism, which works for some people, but not all. Pretending to be angry or disappointed with a sub who has genuinely tried his/her best is a terrible breach of trust, and to do it repeatedly, in my opinion, is a form of emotional abuse.
But you mention miscommunication, and that seems to me to be the heart of the matter. Of all the things both Dom and sub need to master, communication is the biggest. You can't be safe, you can't be honest, you can't be trusting if you can't communicate. No amount of skill with ropes or floggers is worth a hill of beans if you can't communicate.
You can learn a lot by how each of you reacts to miscommunication. Are you respectful when you tell him that you felt his instructions were unclear, or do you whine and accuse? Does he listen when you try to give him honest, respectful feedback, or does he get defensive and impatient?
Both of you need to sit and carefully consider the situation whenever there is a miscommunication or lack of clarity. Doms need to learn how to be better doms, just as we need to learn to improve in obedience and devotion.
If he has a valid reason for being displeased, and tells you so, then your job is listen. In your own mind and heart, think carefully about what has displeased him. Make sure that you have set aside your own ego, your own hurt feelings, and your own desire to be "right." Those are things a submissive needs to let go of if she wants to serve to the best of her abilities.
You mustn't ever be afraid or reluctant to speak up when you feel he's been unfair, but you must be sure you're being honest with yourself, and do it respectfully. And when you are in the wrong, you must suck it up; feel the hurt but don't let it turn you into a useless puddle on the floor. Put that energy instead to making amends and figuring out how you can avoid repeating the behavior that displeased him.