From the outside you are NOT able to see the bolts that attach the wing to the rest of the structure. However you might have seen some screws missing from a wing to body fairing. Missing thse screw does not infringe the safety of said wing structure. As mentioned you may get a little bit vibration but nothing serious at all. Aircraft are allowed to fly with certain panels missing. In this case the panel is still attached to the airframe by two screws so whats the problem?
I've had passengers coming up to me (ground engineer) telling me that they saw a big bolt coming out of the engine pylon. So they feared the engine was going to fall off. But the only thing you see on the outside of a pylon are the screws that hold down the panels. And even between these panels there is no room for a big bolt to fly through.
Please don't make such a fuss about it.