How long after the blisters appeared did you have them swabbed?
It would be really unlikely for this to be hsv2 for a couple of reasons - you already have antibodies for it, and your only risk was oral. Oral hsv2 is rare, and when it does occur, it rarely sheds, rarely recurs, and thus, almost never transmits.
So hsv1 - it could be, but depending on the timing of the swabs, it would be unusual for swabs to miss it. I'd be interested to see what a PCR swab showed - it's more sensitive than a regular swab.
The hsv1 IgG can miss 30% of infections, which is why it still remains a possibility. Given that it was brief and protected, the chances are low, though.
Have they done any other testing? Have you considered trying Valtrex just to see if that helps?