[mware]

Actually I had the opposite happen to me. A student came up after class and said that I gave him credit for an answer he got wrong.

I double checked it, and he was right, I had given him two points he did not earn.

I looked up at him and said,"Two points for honesty", and kept the grade as it was.

[Aggie Mama]

Ha! I do the same thing with my students. They are always amazed at that. :)