good lord, if the mechanic did not test drive, AND duplicate the noise for himself, he needs to go out of biz...
if he said it was a bushing, well there is only a lower control arm on the vehicle with a bushing. i would really need to hear said grinding noise... sure it is not just a loud/harsh squeek?
can you duplicate it by pushing down on the fender?
struts and control arms may squeek very loudly. since the strut is new, that leaves the LCA.... however, swaybar bushings can get pushed out, and the sway bar will hit the bracket and make all kinds of racket.
quick sugggestion... open the hood, and push down on the strut tower NOT the fender to try and duplicate the noise
i am very, very familiar with the suspension on your vehicle.