in my experience its hard to make some one 100% happy with their car when its done. their is almost always something that even if small could have been better. there could be different reasons for it. if its just a finish isue and not rust or anything like that,may be they did think it didnt show and wanted to save you the money of finishing it nice. its always hard to know how perfect to make a car when your the guy doing the work and someone else is paying you.i could spend for ever on my own car making it perfect but if i handed someone the bill for the hours i put in they would probably be surprised at the cost of perfect or worse upset.when someone tells me they want a nice driver not a show car i can guarentee you when they come to pick it up they always expect it to be done to show car standards and will try to find things wrong.so i always just tell everyone i'm doing the best job i can and it will be expensive so if you dont want it that way take it somewhere else, not being ignorant just covering my but and reputation.i painted a car for a guy who wanted a driver not a show car .i had the car blasted and did it on the rotissorie painted the bottom and it looked real good.when he seen it he wanted to know why i didnt wet sand,buff the door jambs and bottom also ,like the outside? i told him that to me a drives dosent have buffed doorjambs and underside its allready nicer than new. but i buffed it all up for him so he was happy with his driver.that was the last time i painted a car that the owner said just make it driver quality.
but if you dropped off the car and said make it as perfect as you can what ever it cost, and it was screwed up then you should be upset tell them it needs fixed see what they tell you.