caught unawares
To be surprised by someone or something. A: "Oh man, I was totally caught unawares when your mother showed up here this morning." B: "I figured as much when she told me that you answered the door in your robe and curlers!"
catch/take somebody unaˈwares
surprise somebody; do something when somebody does not expect it: Her sudden refusal took me unawares.You caught us unawares by coming so early.