Your thinking isn't wrong. A good tech would've had an ear or feal for it. Unfortunately, the days of good techs aren't what they used to be. A test drive should've told them so. They probably just looked at the work order and did the easiest fix to make money. FLAT RATE doesn't ever give the best results.
Been there, done that, have a few t-shirts (that's why I work in power generation now). Good techs will go the extra mile to make sure there isn't a comeback. Unfortunately, it seems as though the comeback game has gotten skewed.........most like everything in today's 1 hurt feeling world.
In the future use your senses, like you did, and just learn what your truck feels,sounds,handles like and you will tune into things amiss.