From what you have written, I suspect your parents love you very much. They held off cashing your check out of fear that you wouldn't have the money.* They haven't asked for their car back. Sure, they don't approve of all your actions, but that's a bit much to hope for. They are trying to protect and guide you, which is a natural parental feeling even when you don't want it.
It isn't easy watching your kids grow up and make mistakes, even if you know intellectually that it's necessary. So, call and see what's up, and try to keep in mind that they might be scared for you. Even if you have everything under control, they will worry... that's what parents do.
My $0.02. Bear in mind I'm an old fart and a parent.
*If you had the money for the check, how could you suddenly _not_ have the money unless you were overdrawing your funds? Just because the money's still in the account doesn't mean you can spend it... sorry if it comes off like a lecture, but I've seen folks get really burned that way, especially with credit cards.