My girlfriend has a 2006 Lexus ES330.

Some idiot bonked it enough in a praking lot to 'dent' in the plastic
bumper on the rear on the corner. And then took off of course.

I took a look at it and it was not hard enough to even come in contact
with the frame underneath, the plastic is not broken, just 'punched'
in. I know something similar happened to my van and I waited until a
hot day and just bonked it back it out with the rounded end of a
crowbar. I suspect the same thing will work here, except I need to be
able to get in there. So I have to remove some plastic bumper spacers
and then am going to lift that portion away from the vehicle and try
to bonk it out. I figure to get a chum to hold it.

So - I figure - warm weather to make it as supple as possible and so
it will not crack. Something rounded not pointed. Someone to hold it
so it does not break on the car. Any other clues?

Also - on the vehicle it has a wiper system that senses when it starts
to rain and adjust the wiper on/off and speed according to the rain on
the windshield. I was wondering what kind of a sensor they use for
this and where it is. It works fine, just curious.

Regards.