A: Can I borrow your key card? I need to go downstairs to pick up my parcel and cannot find mine.

B: Sure. Here you are.

A: I guess I left my key card home in another bag. Sometimes I have a brain fade in the morning and leave things at home.

B: Perhaps you are sleep-deprived and need more rest.

Note: This slang term refers to a “temporary inability to concentrate, think clearly or remember things.” It seems the usage is of British origin and often used by Britons.