be fast asleep

[Theme] Sleep well I fell asleep and didn\'t know what happened be fast asleep; An analogy for pretending to know, or falling asleep and not knowing what happened. When a person was asked about Shirakawa in Kyoto, he mistook it for the name of a river, not knowing it was a place name, and answered, ``I didn\'t know because I passed by by boat at night,\'\' so the lie that he had gone out to see Kyoto was exposed. A proverb based on the story, ``I lost it.\'\'