These guys can't know from taking your history. This is utter BS. Only a tissue sample plus a PCR test of that tissue is going to tell them anything. Anything else is speculation. Given the anatomical site, it is more likely that you are just one of those people that will never definitively know why.

Anything is possible and in cancer there are high likelihood's. As those relate to HPV the likelihood is that the lesion is in the posterior oral cavity, not the anterior tongue. Anterior tongue cancers are not a likely location for an HPV lesion. They certainly could tell if an HPV test was done on any of the removed tissue from your surgery. Confirm with them that that was how they determined it and let them show you the pathology report that says so. Other than that it is a bad guess.