while it sucks donkey balls that you paid good money and the job wasn't done right, and you had to pull the stuff back apart to fix it, it's gotta be of some solace to see the smoking gun. at least now you know for sure!
man, i would be mortified if i'd sent a car out like that. besides be embarrassing, that shows sloppy work.
good work on staying with your hunch and tracking it down. hope the reassembly goes like a breeze!