If those rivets missed the fiberglass there I'd hate to think where else they missed the more important parts. I once saw an aircraft of a canine variety where the aileron control horn in the cabin was bolted to the airframe and the bolt holes in the fiberglass were only half into the fiberglass. Bit hard to explain other than it looked like the pic in the report posted here where the glass has torn away from the rivets as there was not enough "meat" around the bolt holes.