I congratulate you on your work, and your growing understanding. This work takes courage and patience.
First, you have a likely benefit of symptom relief in the long-run by your knowledge of this event and the impact on you. It may not be instant, but it is part of the picture you're learning about your deeper experiences and your "hidden" feelings. This cannot be understated. When there are symptoms, remember these "unseen" experiences and use them to explain why you have symptoms to yourself.
Part of your continued explorations might be knowing that the anger is actually a form of defense so that the sadness is not felt. Or that vulnerability is avoided. These more tender qualities might be meditated with, or journaled in a form of a "gestalt" where you are listening to your sadness and letting it speak to you as sadness in your writing: "I have been around for a long time, and no one has noticed me." This kind of conversation. Listening. Attuning.
This two-way conversation might be done out loud with a couple of pillows, you taking the place of "you" in your normal identity on one pillow, and "sadness" on the other pillow. Switch back and forth and explore talking directly to the other.
Importantly having compassion for yourself in this situation, this event, and the subsequent feelings is probably key, because it has been separated from your awareness.