Can they really invite me separate from my wife?? (Help! Miss Manners!)

Thanks for the clear analysis, tlw. The exact scenario was—

This is why I can’t get too indignant at them. Why it isn’t a clear-cut case of whose fault the screwup was.

Now I’m wondering what to say about it if they ask me the next time I see them.

Odd that another one of my friends, who saw me while I was briefly there, said, “When I saw you, at first I wondered what you were doing here, and then I remembered.” Odd.

We forgot to take back the gift before leaving. Oh well.