Sure, it could be something else, but you need to have the sores swabbed and pcr tested if they show up again. You may want to get an IgG type-specific test done right now for a baseline result and then get another IgG type-specific done in about 10 weeks to see if the result changes.
If this were a primary herpes outbreak, I am a little skeptical it would have cleared up so fast.
Even though you and your partner were virgins and monogamous, your partner could have oral hsv1 and infected you through oral sex. If there was no oral sex and you were both virgins and monogamous, then this was a not a herpes outbreak.