Carrying a passport is a legal requirement in many countries, especially common for tourists. But if I accidentally left it in my hotel? I don't think I would g

Carrying a passport is a legal requirement in many countries, especially common for tourists. But if I accidentally left it in my hotel? I don't think I would get arrested on the spot. Worst case they'd take me to the hotel so I could produce it. I suspect there is more to this story - i.e. they had a reason to think he was an illegal immigrant or on drugs or something - of course that reason could be something racist or completely unfounded, but I presume they don't just arrest anyone who forgets their ID.