Is it really the thought that counts?

While having a couple drinks with friends the other night I was reminded of a moment from my past that still bothers me. 
A few years back, when my mother in law was still on speaking terms with our family, I got the mail one day at the beginning of May and in it was a Mother's Day card to me from her.  Not to surprising right??? Well this particular year not only was no gift included with this card (as had been in the past) this card was made out to me in my maiden name.
My husband (ever the optimist) told me I should be happy she thought of me.  I am still bent on this one.  Am I justified? Was it an innocent mistake?  Maybe I am just too up tight.