Many years ago I worked as a health inspector. Some of the places I inspected had irregular or non-regular business hours, so I would have to schedule an inspection time with them; a couple weeks notice.
To be clear: they would know exactly when I was showing up and what I was going to be inspecting.
You'd think, with two weeks notice and all the foreknowledge, that they'd make an effort to pretend to clean up or fix things. Nine times out of ten, they wouldn't do anything before I arrived. They were always totally surprised that I would cite them or shut them down. Most of my findings were for easily correctable (or concealable) violations.
It's like they thought that because they knew about a "surprise" inspection, it made them immune from the normal regs and laws.
Why do I bring this up? It's just to show that even when someone knows something is coming, they can still be surprised.