Not sure if this is a bug, or just an oversight, and I'm not entirely sure this is actually related to gavin, but a cursory Googling seems to indicate it is (if Google is a dirty liar, I appologize)
So, it seems that I have stumbled across the very end of Gavin's personal quest, without having actually recruited Gavin at all. I ended up wandering into a house in Beregost, as I do quite enjoy just barging into people's houses and taking their stuff. In this house, I faced a really tough encounter with a cleric who summoned three waves of skeletons, and three (what I assumed to be) fighters.
Then, I went to the top level, and a woman named Valeria began talking to me about missing villagers, and I was very, very confused.
SO, yeah, if this really is the end of Gavin's personal quest, and I'm not supposed to be here, that's kind of an issue.