We just discovered that 3 nights ago our daughter snuck out her window with her 21 year old boyfriend while he was up visiting. If she is taken to the doctor for exam to see if still a virgin or not do they have a legal obligation to tell me due to him being 21. And if there is any legal action that can be taken against the 21 year old boyfriend.

Many states have changed the law to a minor 16 to 18 can be with someone up to 4 yrs older or adult.
From what I have looked up North Carolina age of consent is 16.

Under North Carolina law, the age of consent is 16 for both men and women. This is the age at which a person may legally consent to sex with an adult. This covers heterosexual acts. The state doesn’t have a valid law that covers age of consent for homosexual acts.. . Age of Consent Laws - Family Laws - Labor Law Talk Blog (http://blog.laborlawtalk.com/category/family-laws/age-of-consent-laws/)

I have checked other sites as well.

Unfortunately for the parents many states now have schools passing out condoms and having their doctors tell them it is okay to have sex at young ages. Then they wonder why teens and teen age pregnancies are the way they are today.

It appears that in NC that a 17 year old can decide to legally have sex.

It may be worth a talk with the DA to see if there is any new laws or other charges, such as interfering with custody, a adult taking your minor child out without permission. That they may be able to charge.

You may also get a restraining order or order of protection against him to keep him away in the future

If she waited till she was 17 yo then count yourself lucky.

... do they have a legal obligation to tell me due to him being 21. ...

Who? The doctor? I think not.