What was unusual was that my license plate assembly popped half off the bumper. Apparently, it had been *glued* into place instead of bolted, and the glue had rotted away or something, so that that light tap was enough to dislodge it.
Don't ask me why it was glued on -- it seems like a bizarre choice, unless driling bolt holes would have weakened the integrity of the bumper or something.
But I had some 'mighty putty' lying around the house (I'd bought some at Walgreens while shopping for dental floss or something) so I decided to glue it back into place. The stuff's kind of neat -- it's like normal two-component superglue, but they make it safer to handle by making it work reeeeeally slooooowly. As in, two minutes of kneading to get it to mix, and an *hour* before it sets.
Which was inconvenient, because the plate assembly really doesn't want to be in contact with the bumper. It's not the right shape -- the glue was holding it on by bending it slightly. So I had to scavenge a bucket from the dumpster to hold it in place long enough, because I was *not* going to be standing out there for an hour.
After letting it set, the thing did seem to be on fairly snugly, but there's an annoying amount of 'flash' where I decided to glue the corners into place separately, just to make sure it was really on there. So I looked in the instructions about removing the flash... 'Before the putty sets, you can...'
Well, the car's already got polka dots of sap, ground-in dirt and splattered asphalt... yeah, there's a reason I don't worry so much about scratches.