Attn Dentists: how would your office handle a scheduling mistake?

I have been seeing my dentist for ten years. I schedule my next appointment at the end of my last one. I’ve been doing it that way for ten years. Last week I go in for my appointment and they tell me I don’t have an appointment. I explain I scheduled the appointment 6 months ago at my last appointment. They tell me they tried to call me in May but I was unreachable. I have no missed calls, no voicemails, and no texts from them. (They do have text reminders for appointments but I didn’t think that not receiving a reminder meant I didn’t have an appointment) I confirm they have the right number. They do. They tell me that the person who schedules appointments retired and that’s probably why there’s no appointment.

They say the next appointment is a month away. No apology. No “let me check to see if we can do something”. They made me feel like it was my fault - sorry not sorry. I left without saying anything out of frustration. I was so angry. I took a day off work. I drove 30 minutes to their office and they just had an “oh well” attitude.

Do all dentist offices handle patients this way? What would your office have done? Is that the norm nowadays?