Not really sure. Maybe they were just trying to increase your knowledge. If you tested at the right time (waited long enough) or if you had an active sore that they swabbed, then your test results are probably accurate. Is there a reason you are worried about it?
Have you had sores or blisters that you are concerned about, since you were being checked, or were they just randomly checking for herpes? If you don't have an active breakout, you can go years without a diagnosis. I knew I had herpes for years, so when I was in the office during an outbreak, I specifically asked to be checked. I've been married for many years, and my husband knows, but if you are planning to have children, your OB needs to know to be sure you don't have an outbreak during a vaginal delivery, because your newborn could also be susceptible to contracting it, even possibly in the eyes, which could blind a newborn. I'm not telling you this to scare you, but to educate you.