I once packed up my laptop and took it with me when I went to the bathroom at a coffee shop even though at the very next table were four uniformed police officers.
I try to act normal when police officers are around. I never know when I'm going to see the same police officer again. That would extend to packing up my stuff and taking it with me. Also what if the police officers left while I was gone?
In retrospect, that was a little silly.