What kind of testing did you have done? If it was a swab test where they cultured the sore, those aren't always accurate. A lot depends on timing (how long after you got the sore did you get it cultured, etc.), had the blister already popped, etc.
You can ask for a type specific IgG blood test now. Make sure the doctor does this one, and not any others. If you had an IgG test before, and it was negative then, it may have been too soon for antibodies to appear. If you didn't, and it's positive for type 1 now, you won't be sure if that's an oral infection you already had (think cold sores), or a new genital type 1 infection if your partner performed oral on you.
Good luck!
That is confusing. You can swab the blister again but the fact that your only exposure happened and you tested neg. after, that's a good sign.