Q: Several weeks ago, I had a luncheon appointment with a friend. The plans were made two weeks before and I had reconfirmed the engagement by telephone two days prior to the date. I arrived at the restaurant on time and waited outside as we had arranged.

When she had not appeared after half an hour, I called her office, expecting to hear that an important project had delayed her. Instead, her office mate informed me that she had left for lunch over an hour ago with someone from another office and was expected to return momentarily. I left a message that I had been waiting.

I am a housewife and live in the suburbs. In order to meet her, I had to take two buses and the subway. Aside from the luncheon date, I had little reason to come to the city. I valued this woman's friendship as evidenced by my willingness to spend several hours traveling for an hour's lunch. I have been waiting to no avail for her to call with an apology or at least an explanation.

Miss Manners, do you agree with my husband, who says that I should just forget the friendship? Or do you think that it might be proper for me to write or telephone her? If so, what would be appropriate to say? I do not have many friends, since I do not have many opportunities to meet people, and I feel dreadful about losing a friendship.

A: One always gives a friend a chance to explain--and one accompanies it with the warning that the explanation had better be good and also abject.

"Good grief--what happened to you? I was sure you had been run over--I knew you wouldn't leave me standing on the sidewalk like an idiot--WHAT HAPPENED?"

The only acceptable answer is, "Thursday? Was that supposed to be Thursday? Oh, no! I had it under the wrong month in my calendar. Will you ever forgive me? How could I have been so stupid?" and so on.

Incidentally, Miss Manners has picked up a hint that you suspect your friend of treating your schedule carelessly because you are a housewife. You had better throw her a chance to clear that one up, too ("Surely you didn't think my time didn't matter?" "No--how could you even think such a thing?") because friendships can only exist on terms of mutual respect.

Feeling incorrect? Address your etiquette questions (in black or blue-black ink on white writing paper) to Miss Manners, in care of this newspaper.

Copyright (c) 1983, United Feature Syndicate, Inc.