I see the English renders baadi-sachi as 'patdown', which suggests a less intrusive investigation than I was envisioning. But still, my amateur assassin, if you're off to um well, off someone, and have been told he has security who will search you and your luggage, do you think it sufficient to wrap your gun in a plastic bag and hide it beneath a change of underwear? And why a gun, for pete's sake? Which is a suicide weapon FTR, in case of capture. If your gun is found, do you think you'll be given a chance to use it?
Am not looking forward to reading this section, but hey, maybe in Murakami's world they do things this way.
Also maybe my language level, but Tengo's unlovely Mephistopheles who calls him late at night with obscure threats sounds much more sinister in Japanese than in English.