So I was installing my bumper plugs when I noticed how easy it is to drop the threaded inserts inside the bumper with the plugs (if this happens, you have to remove the bumper ). I noticed that if you so happened too push in the threaded inserts and it has not fallen down yet, I found it easy to get the screw that was used for the license plate frame and use it to push it back in. And then just try putting the plug back in.

I'm pretty sure you have figured this out, but if there are people who don't know, now you know.