If my memory serves me from my public health days, the interface between teeth and gums is considered and has shown to be a potential portal of entry. I'm not remembering about whether stomach acid neutralizes rabies, but abrasions, lesions etc within the alimentary canal cannot be excluded as possibilities as well. The cat will have to be quarantined. Public health might want to examine the brain tissue of the bat. It was not good to use a towel because it is absorbant. It should be properly disposed as in incinerated. Public Health or Animal Control might do that for you. Wear gloves. If any tools were used like a shovel or something, they should be sanitized using a strong bleach solution. Your son might have to undergo shots as a precaution. This can be avoided if the bat can be found and tested to be negative. Although the bat might be damaged or ill with something else, since bats are known carriers, you have to play worst case scenario to protect your son. A less remote possibility is secondary contact by family members with your cat who might be infected. Be careful, best wishes.
