You're probably not looking in the right place. Crawl up under the dash on the driver side and look up at the inside portion of the cowl just above the inner cowl panel. You will see a second structural/reinforcement looking piece that extends from the door pillar almost to the firewall. That piece has been pre-drilled with two holes, in a vertical pattern.
Those holes are there specifically for one reason... to act as guides for drilling the holes in the cowl for those mirrors. Unless your friend's truck has suffered catastrophic damage, those pieces are there... and if I'm not mistaken the procedure for installing those mirrors is covered in the Assembly Manual.
