the reason that you would see "foaming of the mouth" is because with a rabies infection, it attacks the nervous system, the first thing to go is ones ability to swallow, thus all saliva must go somewhere, hence appears there is a foaming, and then each part of nervous system becomes affected, thru most of it, still keeping your mind, and most horrible way to die, and people still die every year from rabies. There are aproximately 50 different strains of rabies, most common becoming infected within 5 days. Once one has been bitten by wildlife, and drawing blood, the creature should be caught and taken to animal control or health dept. for further instructions. If the creature isn't caught then one should go to the hosp. or clinic to take the rabies shot, which are no longer in the stomach, depending on the type of bite, type of creature will determine the number of shots in the arm. depending on your area, typically squirrels are fairly safe from having rabies,most notorious animals are bats, raccoons and skunks.
With your squirrel bite i would still consult with a doctor. Once you have one symptom of rabies it is not currable. you will die. there is one case of a person that has survived, last i heard she was alive, but unable to function, completely diabled and lives in a wheelchair. She was young girl that found a bat on the church floor during surfaces and handled it, keep in mind that rabies is in the saliva and not just in a bite, saliva from an infected animal can cause an infection in an open cut. I worked this industry for years.