I just had two rear caps replaced at the dealer, just over a week after taking delivery. The caps were lost within two days of getting the car. I glanced at the replacement caps and they don't seem to have provision for the steel ring inside to keep tension on the tabs against the inside of the wheel bore. Maybe I just didn't see it...
I don't know about super glue - you want to be able to remove the caps if necessary. Maybe used sparingly and in a way that it could be cut/trimmed to allow the cap to come out. A very small dab of silicone adhesive applied from the inside with the wheel off the hub may be a good option. For now I'll just pound the caps in after each drive too.
