You cant test for rabies without euthanasing the animal.
"...to rule out rabies, the test must include a full cross-section of tissue from both the brain stem and cerebellum." - https://www.cdc.gov/rabies/php/laboratories/diagnostic.html
He had just taken in a raccoon so the squirrel could have gotten it from that, and they don't know if the owner had been lying about taking it outside.
This is all the owner's fault for not taking the squirrel to a proper animal sanctuary.
I have no idea who either of these people are.