If the blood test was an IgM, it could easily be a false positive. Even IgG tests have false positives. The HSV 1 antibody test misses 1 our 4 HSV 1 infections. As you can tell, these blood tests are not perfect. The Valtrex would not impact the current test because he had plenty of opportunity to develop antibody before starting the medicine. While it is possible that he might have HSV 1 and the test missed it, I think it is really unlikely he has HSV 2.
Have you been tested?