Methinks prj is being a bit harsh about the product and usage.
Trek is going to stand behind the product within their warranty guidelines. I would think that the mechanic could have been a bit kinder considering that you helped keep him there another few days with your purchase and required service on a new bike...which is always needed a bit after your break in ride(s) on any level bike. As was stated above though he doesn't have to have people skills to be a good mech. Perhaps someone else had just crapped in his Oaties about something else, who knows.
I would expect that some minor item worked loose and it will be as good or better than new. Let us know.