Chewed on it, didn’t knock it off.
Bummer. Squirrel may have seen reflection, or just curious. Birds have been known to attack mine.
I have found a replacement part for the damaged “bubble”. I had to order a bag of 20 of them.
In ebay, “20pcs PIR Optical Fresnel Lens for Human Body Pyroelectric infrared Sensing”
the size is:018090 black.