I deal with this very thing on a daily basis..Why just the other dayWe had a customer come back after the rear brake job and rotors was done on their BMW, with the car making a horrible noise...
We get it in the shop and the first thing I notice is the calipr braket bolt had fallen out causing the caliper to scrub the inside of the wheel...Of course this should be a "Warranty" thing as we looked up who did the job and guess what??? (After hearing from the boss how I need to have five cars being worked on as that's how he did things when he was "On the line" as a tech), it his fault....
The Customer was charged again for the repair as true, it had been over 1 year (Out of our warranty), but Do I call the customer and tell them? Or do I keep my job and not say anything.....
It's a tough call when you need your job....