Honestly they got their hands full, they are not going to go out of their way to find you and take it. You don't have to give them details if you are that worried. It doesn't to hurt to call and ask a few questions.
"Hi, a snake was left at my friends house. He no longer wants to care for it and it has been there for oh so much time. What can he do? The owner says he is coming back but..." you get the idea.
In my area, if someone leaves an animal with you for over a certain amount of time, you are considered responsible for it and can turn it over to a rescue or someone else if you so please. Just check it out, or don't.
You seem like a decent person who is rightly upset over an awful situation. It might help you to know what your rights are in this situation.