Forgetting Appointments: What to Do When You Miss One?

Has anyone missed appointment of any kind and only realize alot later? I usually never miss appointment because I'm extremely anxious on making sure my appointments are all on my calendar on my phone and it gives me reminders 1 week before, 2 days before, the night before and depending on how long it would take me to get there I would schedule a reminder to maybe an hour before. I am seeing a psychiatrist who is a ton better than any other doctor I've seen. It is a online zoom call appointment. Usually I have a online record for each health care place or even my gym so my appointments show up on there and I just add it to my calendar and set reminders. This practice doesn't really have that system. So basically I forgot to add my appointment. I thought it was next week but it was actually last Thursday. I got a call from them 2 days before appointment to confirm and I guess I did but I don't remember it. This week is generally stressful for me because my dad went overseas all of a sudden and I have to work odd hours at the business he has. I only realized I missed my appointment when I got a missed appointment fee bill in the mail this morning. I feel embarrassed now because I tend to never miss appointment and am always early because otherwise I get intense anxiety. I don't know how to face the doctor next time. I know it's not an excuse but I hate that this can happen and I would have to pay quite a bit out of pocket for it because of my adhd and stress. Any similar experiences?