go blank
also blank out1. to forget He let his mind go blank and kept on walking, thinking about nothing at all.
2. to become unconscious
He remembers trying to get up, and then he went blank until he woke up the next morning with a roaring headache. Usage notes: sometimes used in the form everything went blank (someone became unconscious): I heard a noise behind me, and then everything went blank.
Related vocabulary:
black out 3. to stop receiving a television picture There was a popping sound, and then the TV screen went blank.