In the long run, going without thyroid meds can cause damage to the heart, but it should take longer than a week. After missing more than a day, it can take up to 3 months to get thyroid levels regulated again, so that’s why it is important to not miss a dose. Just 2 days of missing doses can cause symptoms for a month or more.
I agree that your vet was extremely unprofessional. Maybe if you had called them and explained your issues, they could have worked with you and given you enough to get you through, but he would not, he had no cause to complain at all. And no matter what, he had no cause for his actual behavior.
