BMW knock sensor replacement

The guy collected my car around 10.30 (slightly later than expected but traffic was heavy). Was told it maybe closer to 7pm when it would return.(Despite being texted earlier in day saying it would before.) By 8pm there was no sign and no one to get in touch with!! Panic started rising. Had I been had or something similar? At 9pm the door bell went - expecting the worst, I was surprised to find the guy from earlier looking for somewhere to put car keys. Relief!! Driver apologised over the lateness blaming too much work. At least the car had its service and passed its MOT. So we're good to go.... 👍🏻 But next time a phone call would be appreciated be if you're going to be late!