Green’s Dictionary of Slang

(US) a bluff, a deception, an unpleasant surprise.

1969		Current Sl. IV:1 7: Fake out, n. A bad experience.
1970		(con. 1950s) H. Junker ‘The Fifties’ in Eisen Age of Rock 2 (1970) 101: What a fake-out.
2005		E. Weiner Big Boat to Bye-Bye 81: ‘What’s the point of this fake-out?’.