Miss Manners: The hostess sent a shocking message about my lack of gratitude

Dear Miss Manners: Less than 48 hours after my husband and I attended a gathering at the home of a couple from our walking group, I received a text from the hostess that read, “I hope you enjoyed the party. Should I assume it was an oversight on your part not to send a thank-you note? We believe we were gracious hosts and would appreciate gracious guests.”