Does a woman's hymen ever grow back?

No, the hymen cannot grow back.

The hymen is tissue surrounding the vaginal opening, it normally doesn't cover much of the vaginal opening and is flexible so can stretch to accommodate penetration. If you go without sex for some time the hymen can return back to it's normal position, like an elastic band returning to normal after being stretched. The hymen can tear if penetration is rough or forced, the hymen will heal and remains where it is around the vaginal opening, but it will remain torn and not grow back.

The hymen cannot grow back once it has been stretched open. If you don't have sex for a very long time you will notice a difference when you do have sex again (it may feel a bit difficult at first) but you will not re-lose your virginity. ~ T It depends, I didn't have sex for two years and when i had sex again I bled. But then again I only was with 1 guy and I could count the number of times i had sex on one hand. I think it also depends on how rough the guy is too. My GYN told me it's not uncommon.