My answer is not giving you specific legal advice and does not invoke any form of attorney-client relationship, including the attorney-client privilege.
The short answer is that this happens more often than not on the Internet. If the information they find about you is listed on a public source that anyone could request information from and receive it, they can legally request the information.
As a pertinent example, I just found my profile here on Avvo and I didn't give them rights to post it; however, my information was on the IL attorney's registration website... and anyone could get at it, so they were able to pull it without having to contact me as this information is public knowledge.
Skip-trace/background check services pull from both public and private sources including websites to get your background. If you don't want your information listed, some public information websites may have request mechanisms in place to ask for information removal. But in many case, where your info is a matter of public record, they don't offer this.
Unfortunately, the Internet with all its convenience for things we need also makes it easier to get information we would not want so readily available.