I did this in a Parlour last year when I'd booked a girl who only works there one day a week. Because I'd not punted in a Parlour for about 6 - 7 years, I'd forgotten to check with the Parlour before I set off on the day of the appointment and only discovered when I got there that she'd rung in sick before they opened that morning.
I was offered either of the two other girls who were on that day's rota [it was a quiet time of day!], but neither of them appealed that much to me [they were a bit young for my tastes] so I said "Thanks, but no thanks" and walked out. No recriminations for me, either.