I'll start off by saying this outright so people know my stance, this may seem like I'm defending n5m/42g but I'm really not. I think n5m/42g is so far inferior to Ginza, I see no reason for me to visit these establishments anymore.
So to play devil's advocate, since you said you saw the girl you booked in the corridor, i see 3 reasons why the situation you described could have happened.
- The girl actually felt sick and wanted to go home right after the punter before you and cancelled (you were just unlucky)
- Reception accidentally double booked and made a random excuse, it happens, even Ginza does this sometimes (although very rarely)
- As you described, the girl saw you and didn't want to see you for whatever reason/she shadow banned you from seeing her and told the reception. The reception, didn't want to hurt your feelings said she cancelled because she is sick
Again, i'm just playing devils advocate here, i don't actually know what happened but i find it unlikely it was some sort of unethical booking practice ( I do believe some shops do this, but prob not n5m).
"Never attribute to malice that which can be adequately explained by stupidity"