They do not have a sense of humor. This would be a cute way of writing a blog post about your day(s) spent in detention before being sent back to your country of origin/citizenship.
I'm sorry I sound so naive, but I'm still incredibly flabbergasted by this.
This stuff is not ok. Not at all.
1) These are not the police. Police are trained law enforcement officers. These are customs and immigration employees. They get training, but it's more important that they can get a security clearance.
2) Can you think of a reason for having a file of white noise that you could explain to this person that they would understand and believe?
You really don't have many rights outside immigration/customs. "Probable cause" is "he acted weird." Cars have been destructively disassembled for less.
If they look at a computer based on information provided by a person entering the country, they have to have clearance. Uncleared or precleared people will often hang out over the shoulder of someone with clearance, so it's not really that "secure", but it ensures that queries are handled by cleared personnel.