I would likely keep the appointment as well. With that being said, if you run into something like this again, and rebooting with the two buttons doesnt work (pressing the brake pedal doesnt add anything to that process), try doing a POWER OFF from the menu, and let the car sit powered off at least 10-15 minutes. Tesla will say a shorter period of time, but you want to ensure that the car also goes to sleep when powered off.
I do this after every update, and I dont ever have any of the problems many others report:
1. Go to car, open drivers car door, get it, but DONT close car door behind me
2. Navigate to the POWER OFF command in the menu (I think its under security, but you will find it in one of the bottom menu choices)
3. When the car powers off, exit the car through the STILL OPEN car door and close the door.
4. Dont touch the car until the next time I am ready to drive, whenever that is.
By having the door open I can power off the car and get out and close the door, without sitting in the car with it powered off. If you power it off while in it, you need to wait to touch anything until it goes to sleep, and that can feel like forever if you are sitting there ("watched pot" and all that).