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Some greater context might be needed, but I thought of:
Entertainingly Wrong — if it's meant to be comedic or entertaining. (A friend died) + (Friend's father is at a funeral) = (That friend died). Hilarity Ensues.
Poor Communication Kills - Probably better suited for a more dramatic angle where this wrong assumption causes legitimate grief. And it could have been prevented by the father specifying whose funeral he was at.
Edited by KD
Having heard a friend died, a character calls the father of the friend. The father was at a funeral of someone else entirely; however, the person who answers the phone says (totally truthfully) that the father is at a funeral, and the caller thinks the friend died.