Who told you that you had the swollen node? Has a doctor examined that? You really should let a doctor make that determination. Loads of things can cause swollen glands, including stress. It might not even be a gland you're feeling, but something else, so definitely get it checked out.
The WB doesn't miss 8% of infections - the hsv2 IgG does. Is that the test you had? Can you get a copy of the results?
What was your low risk contact? Oral sex? Something else? That would help me answer your questions, and let you know what infections you might be at risk for.
Have you had any other testing done, like chlamydia or gonorrhea? I can't say if you were at risk for those without knowing what your encounter was, but if you are concerned about mycoplasma, you'd probably be at risk for gonorrhea and chlamydia.
So can you tell me what your exact test for herpes was, and what your encounter was, and what tests you've had done? That would be really helpful. :)